abdominal ultrasound - society of radiological...

Abdominal Ultrasound

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For Churchill Livingstone

Commissioning Editor: Dinah ThomDevelopment Editors: Kerry McGechieProject Manager: Morven DeanDesigner: Judith Wright

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Abdominal UltrasoundHow, Why and WhenSECOND EDITION

Jane A. Bates MPhil DMU DCRLead Practitioner, Ultrasound Department, St James’s University Hospital, Leeds, UK

E D I N B U R G H L O N D O N N E W YO R K O X F O R D P H I L A D E L P H I A S T L O U I S S Y D N E Y TO R O N TO 2004

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CHURCHILL LIVINGSTONEAn imprint of Elsevier Limited

© Harcourt Brace and Company Limited 1999© Harcourt Publishers Limited 2001© 2004, Elsevier Limited. All rights reserved.

The right of Jane Bates to be identified as author of this work has been assertedby her in accordance with the Copyright, Designs and Patents Act 1988.

No part of this publication may be reproduced, stored in a retrieval system, ortransmitted in any form or by any means, electronic, mechanical, photocopying,recording or otherwise, without either the prior permission of the publishersor a licence permitting restricted copying in the United Kingdom issued bythe Copyright Licensing Agency, 90 Tottenham Court Road, London W1T4LP. Permissions may be sought directly from Elsevier’s Health SciencesRights Department in Philadelphia, USA: phone: (+1) 215 238 7869, fax:(+1) 215 238 2239, e-mail: [email protected]. You may also complete your request on-line via the Elsevier homepage (http://www.elsevier.com),by selecting ‘Customer Support’ and then ‘Obtaining Permissions’.

First edition 1999Second edition 2004

ISBN 0 443 07243 4

British Library Cataloguing in Publication DataA catalogue record for this book is available from the British Library

Library of Congress Cataloging in Publication DataA catalog record for this book is available from the Library of Congress

NoteKnowledge and best practice in this field are constantly changing. As newresearch and experience broaden our knowledge, changes in practice, treatmentand drug therapy may become necessary or appropriate. Readers are advised tocheck the most current imformation provided (i) on procedures featured or(ii) by the manufacturer of each product to be administered, to verify therecommended dose or formula, the method and duration of administration, andcontraindications. It is the responsibility of the practitioner, relying on theirown experience and knowledge of the patient, to make diagnoses, to determinedosages and the best treatment for each individual patient, and to take allappropriate safety precautions. To the fullest extent of the law, neither thepublisher nor the authors assumes any liability for any injury and/or damage.

The Publisher

Printed in China

ThePublisher's

policy is to usepaper manufactured

from sustainable forests

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Contents

v

Contributors vii

Preface ix

Abbreviations xi

1. Optimizing the diagnostic information 1

2. The normal hepatobiliary system 17

3. Pathology of the gallbladder and biliary tree 41

4. Pathology of the liver and portal venous system 79

5. The pancreas 121

6. The spleen and lymphatic system 137

7. The renal tract 153

8. The retroperitoneum and gastrointestinal tract 195

9. The paediatric abdomen 215

10. The acute abdomen 243

11. Interventional and other techniques 253

Bibliography and further reading 275

Index 277

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Contributors

vii

Rosemary Arthur FRCR Consultant RadiologistDepartment of X-ray & Ultrasound, The GeneralInfirmary at Leeds, Leeds, UK

Simon T. Elliott MB ChB FRCR ConsultantRadiologist Department of Radiology, FreemanHospital, Newcastle-upon-Tyne, UK

Grant M. Baxter FRCR Consultant RadiologistWestern Infirmary University NHS Trust,Glasgow, UK

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Ultrasound continues to be one of the mostimportant diagnostic tools at our disposal. It isused by a wide range of healthcare professionalsacross many applications. This book is intended asa practical, easily accessible guide to sonographersand those learning and developing in the field ofabdominal ultrasound. The most obvious draw-backs of ultrasound diagnosis are the physical lim-itations of sound in tissue and its tremendousdependence upon the skill of the operator. Thisbook seeks to enable the operator to maximize thediagnostic information and to recognize the limi-tations of the scan.

Where possible it presents a wider, more holisticapproach to the patient, including presentingsymptoms, complementary imaging procedures

and further management options. It is not a com-prehensive account of all the pathological processeslikely to be encountered, but is intended as aspringboard from which practical skills and clinicalknowledge can develop further.

This book aims to increase the sonographer’sawareness of the contribution of ultrasound withinthe general clinical picture, and introduce thesonographer to its enormous potential.

The author gratefully acknowledges the helpand support of the staff of the UltrasoundDepartment at St James’s University Hospital,Leeds.

Leeds 2004 Jane Bates

Preface

ix

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Abbreviations

x

ADPCDK autosomal dominant polycystic disease of the kidney

AFP alpha-fetoproteinAI acceleration indexAIDS acquired immune deficiency

syndromeAIUM American Institute for

Ultrasound in MedicineALARA as low as reasonably achievableALT alanine aminotransferaseAP anteroposteriorAPKD autosomal dominant (adult)

polycystic kidneyARPCDK autosomal recessive polycystic

disease of the kidneyAST aspartate aminotransferaseAT acceleration timeAV arteriovenousBCS Budd–Chiari syndromeCAPD continuous ambulatory

peritoneal dialysisCBD common bile ductCD common ductCF cystic fibrosisCT computed tomographyDIC disseminated intravascular

coagulationDICOM Digital Imaging and

Communications in MedicineDMSA dimercaptosuccinic acid

DTPA diethylene triaminepenta-acetic acid

EDF end-diastolic flowERCP endoscopic retrograde

cholangiopancreatographyESWL extracorporeal shock wave

lithotripsyEUS endoscopic ultrasoundFAST focused assessment with

sonography for traumaFDA Food and Drug AdministrationFPS frames per secondHA hepatic arteryHCC hepatocellular carcinomaHELLP haemolytic anaemia, elevated liver

enzymes and low platelet countHIDA hepatic iminodiacetic acidHPS hypertrophic pyloric stenosisHV hepatic veinINR international normalized ratioIOUS intraoperative ultrasoundIVC inferior vena cavaIVU intravenous urogramKUB kidneys, ureters, bladderLFT liver function testLPV left portal veinLRV left renal veinLS longitudinal sectionLUQ left upper quadrantMCKD multicystic dysplastic kidney

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ABBREVIATIONS xi

MHA middle hepatic arteryMHV middle hepatic veinMI mechanical indexMPV main portal veinMRA magnetic resonance angiographyMRA main renal arteryMRCP magnetic resonance

cholangiopancreatographyMRI magnetic resonance imagingMRV main renal veinODS output display standardPAC photographic archiving and

communicationsPACS photographic archiving and

communications systemsPBC primary biliary cirrhosisPCKD polycystic kidney diseasePCS pelvicalyceal systemPD pancreatic ductPI pulsatility indexPID pelvic inflammatory diseasePRF pulse repetition frequencyPSC primary sclerosing cholangitisPTLD post-transplant

lymphoproliferative disorderPV portal veinRAS renal artery stenosisRCC renal cell carcinomaRF radiofrequencyRHV right hepatic vein

RI resistance indexRIF right iliac fossaRK right kidneyRPV right portal veinRRA right renal arteryRRV right renal veinRUQ right upper quadrantRVT renal vein thrombosisSA splenic arterySLE systemic lupus erythematosusSMA superior mesenteric arterySV splenic veinTB tuberculosisTGC time gain compensationTHI tissue harmonic imagingTI thermal indexTIB bone-at-focus indexTIC cranial indexTIPS transjugular intrahepatic

portosystemic shuntTIS soft-tissue thermal indexTORCH toxoplasmosis, rubella,

cytomegalovirus and HIVTS transverse sectionUTI urinary tract infectionVUJ vesicoureteric junctionWRMSD work-related musculoskeletal

disordersXGP xanthogranulomatous

pyelonephritis

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IMAGE OPTIMIZATION

Misinterpretation of ultrasound images is a signifi-cant risk in ultrasound diagnosis. Because ultrasoundscanning is operator-dependent, it is imperative thatthe sonographer has proper training in order toachieve the expected diagnostic capabilities of thetechnique. The skill of effective scanning lies in theoperator’s ability to maximize the diagnostic infor-mation available and in being able to interpret theappearances properly. This is dependent upon:

● Clinical knowledge—knowing what to look forand why, knowing how to interpret theappearances on the image and an understandingof physiological and pathological processes.

● Technical skill—knowing how to obtain themost useful and relevant images, knowledge ofartifacts and avoiding the pitfalls of scanning.

● Knowledge of the equipment being used—i.e.making the most of your machine.

The operator must use the controls to their besteffect (see Box 1.1). There are numerous ways inwhich different manufacturers allow us to makecompromises during the scanning process in orderto improve image quality and enhance diagnosticinformation.

The quality of the image can be improved by:● Increasing the frequency—at the expense of

poorer penetration (Fig. 1.1).● Increasing the line density—this may be achieved

by reducing the frame rate and/or reducing thesector angle and/or depth of field (Fig. 1.2).

Chapter 1

Optimizing the diagnosticinformation

1

CHAPTER CONTENTS

Image optimization 1The use of Doppler 2

Getting the best out of Doppler 5Choosing a machine 6Recording of images 9Safety of diagnostic ultrasound 10Medicolegal issues 12Departmental guidelines/schemes of work 13Quality assurance 13

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● Using the focal zones correctly—focus at thelevel under investigation, or use multiple focalzones at the expense of a decreased frame rate(Fig. 1.3).

● Utilizing different pre- and post-processingoptions, which may highlight particular areas(Fig. 1.4).

● Using tissue harmonics to reduce artefact (Fig.1.5). This technique utilizes the secondharmonic rather than the fundamental frequency

using either filtration or pulse inversion.1 Thisresults in a higher signal-to-noise ratio whichdemonstrates particular benefits in many difficultscanning situations, including obese or gassyabdomens.

It is far better to have a scan performed properly ona low-tech piece of equipment by a knowledgeableand well-trained operator than to have a poorly per-formed scan on the latest high-tech machine (Fig.1.6). A good operator will get the best out of eventhe lowliest scanning device and produce a resultthat will promote the correct patient management.A misleading result from a top-of-the-range scannercan be highly damaging and at best delay the cor-rect treatment or at worst promote incorrect man-agement. The operator should know the limitationsof the scan in terms of equipment capabilities, oper-ator skills, clinical problems and patient limitations,take those limitations into account and communi-cate them where necessary.

THE USE OF DOPPLER

The use of Doppler ultrasound is an integral partof the examination and should not be consideredas a separate entity. Many pathological processesin the abdomen affect the haemodynamics ofrelevant organs and the judicial use of Doppleris an essential part of the diagnostic procedure.This is discussed in more detail in subsequentchapters.

Colour Doppler is used to assess the patencyand direction of flow of vessels in the abdomen,

ABDOMINAL ULTRASOUND2

Figure 1.1 The effect of changing frequency. (A) At 2.7 MHz the wires are poorly resolved and the background‘texture’ of the test object looks coarse. (B) The same transducer is switched to a resonant frequency of 5.1 MHz.Without changing any other settings, the six wires are now resolved and the background texture appears finer.

Box 1.1 Making the most of your equipment

● Use the highest frequency possible—tryincreasing the frequency when examining thepancreas or anterior gallbladder.

● Use the lowest frame rate and highest linedensity possible. Restless or breathlesspatients will require a higher frame rate.

● Use the smallest field practicable—sectionsthrough the liver require a relatively wide sectorangle and a large depth of view, but when exam-ining an anterior gallbladder, for example, thefield can be greatly reduced, thereby improvingthe resolution with no loss of frame rate.

● Use the focal zone at relevant correct depth.● Use tissue harmonic imaging to increase the

signal to noise ratio and reduce artefact.● Try different processing curves to highlight

subtle abnormalities and increase contrastresolution.

A B

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OPTIMIZING THE DIAGNOSTIC INFORMATION 3

Figure 1.2 The effect of frame rate. (A) 76 frames per second (FPS). (B) 35 FPS—the resulting higher line densityimproves the image, making it sharper.

Figure 1.3 The effect of focal zone placement. (A) With the focal zone in the near field, structures in the far field arepoorly resolved. (B) Correct focal zone placement improves both axial and lateral resolution of the wires.

Figure 1.4 The effect of using post-processing options. (A) A small haemangioma in the liver merges into thebackground and is difficult to detect. (B) A post-processing option, which allocates the range of grey shades in a non-linear manner, enhances contrast resolution and improves detection of focal lesions.

A B

A B

A B

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to establish the vascularity of masses or lesionsand to identify vascular disturbances, such asstenoses. Flow information is colour-coded (usu-ally red towards and blue away from the trans-ducer) and superimposed on the image. Thisgives the operator an immediate impression of avascular map of the area (Fig. 1.7). This Dopplerinformation is obtained simultaneously, oftenfrom a relatively large area of the image, at theexpense of the grey-scale image quality. The extratime taken to obtain the Doppler information foreach line results in a reduction in frame rate andline density which worsens as the colour Doppler

area is enlarged. It is advisable, therefore, to use acompact colour ‘box’ in order to maintain imagequality.

Power Doppler also superimposes Dopplerinformation on the grey-scale image, but withoutany directional information. It displays only theamount of energy (Fig. 1.8). The advantage ofthis is that the signal is stronger, allowing iden-tification of smaller vessels with lower velocityflow than colour Doppler. As it is less angle-dependent than colour Doppler it is particularlyuseful for vessels which run perpendicular to thebeam, for example the inferior vena cava (IVC).


A

B

Figure 1.5 The effect of tissue harmonic imaging (THI): (A) a bladder tumour in fundamental imaging mode (left) isshown with greater definition and loss of artifact in THI (right). (B) In an obese patient, cysts near the gallbladder (left)are shown in greater detail using pulse inversion tissue harmonics (right). A small nodule is demonstrated in the lowercyst.

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Pulsed Doppler uses pulses of Doppler fromindividual elements or small groups of elementswithin the array. This allows the operator to selecta specific vessel, which has been identified on thegrey-scale or colour Doppler image, from which toobtain a spectrum. This gives further informationregarding the flow envelope, variance, velocityand downstream resistance of the blood flow(Fig. 1.9).

Getting the best out of DopplerFamiliarity with the Doppler controls is essential inorder to avoid the pitfalls and increase confidencein the results.

It is relatively straighforward to demonstrateflow in major vessels and to assess the relevantspectral waveform; most problems arise whentrying to diagnose the lack of flow in a suspectedthrombosed vessel, and in displaying low-velocity


A B

Figure 1.6 The importance of using the equipment properly. (A) Incorrect use of equipment settings makes it difficultto appreciate the structures in the image. (B) By increasing the resonant frequency, decreasing the frame rate andadjusting the focal zone correctly, a small rim of fluid around the gallbladder is seen and the gallbladder wall andvessels posterior to the gallbladder are made clear.

Figure 1.7 Colour Doppler of the hepatic veinconfluence. The right hepatic vein appears red, as it isflowing towards the transducer. The left and middlehepatic veins are in blue, flowing away from thetransducer. Note the peripheral middle hepatic vein,which appears to have no flow; this is an artifact due tothe angle of that part of the vessel to the beam.

Figure 1.8 Power Doppler of the hepatic veinconfluence. We have lost the directional information, butflow is demonstrated in all parts of the vessel—eventhose perpendicular to the beam.

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flow in difficult-to-access vessels. Doppler isknown to produce false-positive results for vesselocclusion (Fig. 1.10) and the operator must avoidthe pitfalls and should ensure that the confidencelevels are as high as possible (see Box 1.2).

CHOOSING A MACHINE

The ultrasound practitioner is confronted witha confusing range of equipment and choosingthe right machine for the job can be a dauntingtask.

An informed and useful choice is more likelywhen the purchaser has considerable experiencewithin the particular clinical field. Many machines,purchased in the first enthusiastic flush of settingup a new service, for example, turn out to beunsuitable two or three years later.

Mistakes are made by insufficient forward plan-ning. A number of machines (usually at thecheaper end of the market), though initially pur-chased for specific, sometimes narrow, purposes,end up being expected to perform more complexand wider-ranging applications than originallyplanned.

Take careful stock of the range of examinationsyou expect your machine to perform. Future devel-opments which may affect the type of machine youbuy include:

● Increase in numbers of patients calculated fromtrends in previous years.


A B

Figure 1.9 Flow velocity waveforms of hepatic arteries. (A) High-resistance flow with low end-diastolic flow (EDF)and a dichrotic notch (arrowhead). The clear ‘window’ during systole (arrow) indicates little variance, with the bloodflowing at the same velocity throughout the vessel. During diastole, the area under the envelope is ‘filled in’, indicatinggreater variance in flow. (B) By contrast, this hepatic artery trace indicates low-resistance flow with good EDF and nonotch. Variance is apparent throughout the cycle.

Figure 1.10 On the left, the portal vein appears tohave no flow (arrow) when it lies at 90˚ to the beam—apossible misinterpretation for thrombosis. When scannedintercostally, the vein is almost parallel to the beam andflow is easily demonstrated.

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● Increase in range of possible applications, animpending peripheral vascular service, forexample, or regional screening initiative.

● Clinical developments and changes in patientmanagement which may require more, ordifferent, ultrasound techniques, for example,medical therapies which require ultrasoundmonitoring, applications involving the use ofcontrast agents, surgical techniques which mayrequire intraoperative scanning, increases ordecreases in hospital beds, introduction of newservices and enlargement of existing ones.

● Impending political developments bygovernment or hospital management, resultingin changes in the services provided, thefunding or the catchment area.

● Other impending ultrasound developments,such as the use of contrast media or

ultrasound-guided therapies which may berequired in future.

The following points are useful to bear in mindwhen purchasing new equipment:

Probe number and design (Fig 1.11)

Consider the footprint, shape and frequenciesrequired: most modern transducers are broadbandin design, enabling the user to access a wider rangeof frequencies. This is a big advantage as this lim-its the number of probes required for a generalservice. A curved array probe is suitable for mostgeneral abdominal applications, operating in the3.5–6 MHz region. Additional higher-frequencyprobes are useful for paediatrics and for superficialstructures. A small footprint is essential if neonataland paediatric work is undertaken and a 5–8 MHzfrequency will be required.

A biopsy attachment may be needed for invasiveprocedures, and, depending on the range of workto be undertaken, linear probes, endoprobes,intraoperative probes and other designs can beconsidered.

Image quality

There are very few applications where this is not ofparamount importance and abdominal scanningrequires the very best you can afford. A machinecapable of producing a high-quality image is likely


Box 1.2 Steps to take if you can’t detect flowwith Doppler

● Ensure the angle of insonation between thevessel and the transducer is <60˚. Colour andpulsed Doppler are highly angle-dependent.

● Ensure the Doppler gain is set at the correctlevel. (Colour and pulsed Doppler gain settingsshould be just below background noise level.)

● Ensure the Doppler power/output setting issufficient.

● Ensure the pulse repetition frequency (PRF) isset correctly. A low PRF (‘range’ or ‘scale’ set-ting) is required to pick up low-velocity flow.

● Ensure the wall thump filter setting is low. (Ifthe setting is too high, real low-velocity flowis filtered out.)

● Use power Doppler, which is more sensitiveand is not angle-dependent.

● Know the limitations of your machine.Machines differ in their ability to detect low-velocity flow.

● If in doubt, test it on a reference vessel youknow should contain flow.

Figure 1.11 Curved arrays (left and centre) suitable forabdominal scanning. A 5 MHz linear array (right) isuseful for superficial structures, e.g. gallbladder andanterior abdominal wall.

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to remain operational for much longer than onecapable of only poor quality, which will needreplacement much sooner. A poor-quality image isa false economy in abdominal scanning.

Machine capabilities and functions

The availability and ease of use of various functionsdiffer from machine to machine. Some of theimportant issues to consider when buying amachine include:

● probe selection and switching process, simulta-neous connection of several probes

● dynamic frequency capability● dynamic focusing control, number and pattern

of focal zones● functions such as beam steering, sector angle

adjustment, zoom, frame rate adjustment,trackerball controls

● time gain compensation and power outputcontrols

● cine facility—operation and size of memory● programmable presets● tissue harmonic and/or contrast harmonic

imaging● body marker and labelling functions● measurement packages—operation and display● colour/power and spectral Doppler through all

probes● Doppler sensitivity● Doppler controls—ease of use, programmable

presets● output displays● report package option.

Ergonomics

Good ergonomics contribute considerably to thesuccess of the service provided. The machine mustbe usable by various operators in all the required sit-uations. There is a significant risk of work-relatedmusculoskeletal disorders (WRMSD)2 if carefulconsideration is not given to the scanning environ-ment (see p. 12). When choosing and setting up ascanning service, forethought should be given notonly to the design of the ultrasound machine, butalso to the seating arrangements and examinationcouch. These should all be adjustable in order tofacilitate the best scanning position for the operator.

Other considerations include:

● System dimensions and steering. Therequirement for the system to be portable, forexample for ward or theatre work, or mobilefor transportation to remote clinics. Machinesused regularly for mobile work should berobust and easy to move.

● Moveable (swivel and tilt) monitor and controlpanel, including height adjustment for differentoperators and situations.

● Keyboard design, to facilitate easy use of therequired functions, without stretching ortwisting.

● Hand-held portable machines are an optionthat may be considered.

Maintenance issues

It is useful to consider the reliability record of thechosen equipment, particularly if it is to operate inout-reach clinics, or without available backup inthe case of breakdown. Contacting other users mayprove useful.

Various maintenance contract options and costsare available, including options on the replacementof probes, which should be taken into accountwhen purchasing new equipment.

Upgradeability

A machine which is potentially upgradeable has alonger, more cost-effective life and will be sup-ported by the manufacturer over a longer period oftime. Consideration should be given to future soft-ware upgrades, possible effects and costs and otheravailable options for the future, such as additionaltransducers or add-on Doppler facilities.

Links to image-recording devices

Most ultrasound machines are able to link up tomost types of imaging facility, whether it be a sim-ple black and white printer or a radiology-widephotographic archiving and communications (PAC)system. There may be costs involved, however, inlinking your new machine to your preferred imag-ing device.


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Equipment manufacturers now follow theDICOM standard. Digital Imaging and Commu-nications in Medicine is the industry standard fortransferring medical images and related informa-tion between computers. This facilitates compati-bility between different pieces of equipment fromdifferent manufacturers and potentially enablesthem to be linked up.

RECORDING OF IMAGES

There are no hard and fast rules about the record-ing of ultrasound scans and departmental practicesvary. It is good practice for departments to haveguidelines for taking and retaining images withinindividual schemes of work, outlining the mini-mum expected.3

The advantages of recording images are:

● They provide a record of the quality of thescan and how it has been conducted: theorgans examined, the extent of the scan, thetype and standard of equipment, the settingsused and other scanning factors. This can be aninvaluable tool in providing a medicolegaldefence.

● They provide an invaluable teaching aid.

● They help to ensure quality control withindepartments: promoting the use of goodtechnique, they can be used to ensure protocolsare followed and provide an excellent audit tool.

● They can be used to obtain a second opinionon difficult or equivocal cases and provide abasis for discussion with clinical colleagues.

The disadvantages are:

● The cost of buying, running and maintainingthe recording device or system.

● The quality of images in some cases may notaccurately reflect that of the image on theultrasound monitor.

● The scanning time must be slightly increasedto accommodate the taking of images.

● Storage and retrieval of images may be time-and space-consuming.

● Hard copy may be mislaid or lost.

● If the examination has been badly performed,the hard copy may demonstrate that too!

Generally speaking the recording of images isencouraged. It reduces the operator’s vulnerabilityto litigation and supports the ultrasound diagno-sis.4 It is only possible to record the entire exami-nation by using videotape, which is rarely practicalin larger departments. The operator must take theresponsibility for ensuring the scan has been per-formed to the required standard; any images pro-duced for subsequent discussion are onlyrepresentative of the examination and have beenchosen by the operator as an appropriate selection.If you have missed a small metastasis in the liverwhile scanning, or a gallstone in the gallbladder,you are unlikely to have included it on an image.

Choice of image-recording device depends onmany factors. Considerations include:

● image quality—resolution, grey-scale, storagelife

● capital cost of the system—including the instal-lation together with the installation of anyother necessary equipment, such as a processor

● cost of film● processing costs if applicable—this includes the

cost of chemicals, the cost of buying and main-taining a processor and possibly a chemicalmixer

● maintenance costs● reliability of the system● storage of images in terms of available space

and cost● location and size of the imaging system● other considerations

—ease of use—mobility—colour capability—ability to produce slides/teaching aids—shelf life of unused film and stored images.

Numerous methods of recording images are availableto suit all situations. Small printers, attached to ultra-sound scanners, are easy to use, cheap to buy and runand convenient if the machine is used on wards ordistant satellite units. However, systems which pro-duce hard copy, however good, are inevitably ofinferior image quality to electronic image capture.


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Multi-system departments are tending towards net-worked systems which produce high-quality images,and can be linked to multiple machines and modali-ties. These are, of course, more expensive to purchaseand install, but are generally reliable and produceconsistent, high-quality image.

Ultimately, the goal of the filmless department isbeing realized in PACS (photographic archiving andcommunications systems). Digital imaging net-works are convenient, quick and relatively easy touse. The image quality is excellent, suffering little orno degradation in capture and subsequent retrieval,and the system can potentially be linked to a con-ventional imager should hard copy be required.

The number of workstations in the system canbe virtually unlimited, depending on the system,affording the operator the flexibility of transmit-ting images immediately to remote locations, forexample clinical meetings, outpatient clinics, etc. Itis also possible to download images from scansdone with mobile equipment, remote from themain department, on to the PACS.

Digital storage and retrieval avoid loss of filmsand afford considerable savings in time, labour andspace. Increasingly it is also possible to store movingclips—useful for dynamic studies such as thoseinvolving contrast agents and for teaching purposes.

Many systems also incorporate a patient regis-tration and reporting package, further streamliningthe ultrasound examination. Not all systems storeimages in colour and there are considerable differ-ences between the facilities available on differentsystems. The potential purchaser is advised to plancarefully for the needs of the ultrasound service.

The capital costs for PACS are high, but thesecan, to a certain extent, be offset by subsequentlylow running costs and potential savings in film,processing materials, equipment maintenance, andmanual storage and retrieval.

SAFETY OF DIAGNOSTIC ULTRASOUND

Within the field of clinical diagnostic ultrasound,it is currently accepted that there is insufficientevidence for any deleterious effects at diagnosticlevels and that the benefits to patients outweighthe risks. As new techniques and technologicaldevelopments come on to the market, new bio-physical conditions may be introduced which

require evaluation with regard to safety5 and wecannot afford to become complacent about thepossible effects. The situation remains under con-stant review.

Several international bodies continue to considerthe safety of ultrasound in clinical use. TheEuropean Federation of Societies for Ultrasound inMedicine and Biology (EFSUMB) has confirmedthe safety of diagnostic ultrasound and endorsed its‘informed’ use.6 Whilst the use of pulsed Doppler isconsidered inadvisable for the developing embryoduring the first trimester, no such exceptions arehighlighted for abdominal ultrasound.

The European Committee for UltrasoundRadiation Safety (ECURS) confirms that no dele-terious effects have yet been proven in clinicalmedicine. It recommends, however, that equip-ment is used only when designed to national orinternational safety standards and that it is usedonly by competent and trained personnel.

The World Federation for Ultrasound inMedicine and Biology (WFUMB) confirms thatthe use of B-mode imaging is not contraindicated,7concluding that exposure levels and durationshould be reduced to the minimum necessary toobtain the required diagnostic information.

Ultrasound intensities used in diagnostic ultra-sound vary according to the mode of operation.Pulsed Doppler usually has a higher level than B-mode scanning, which operates at lower intensi-ties, although there may be overlap with colour orpower Doppler.

The American Institute for Ultrasound inMedicine (AIUM) has suggested that ultrasound issafe below 100 W/cm.8 This figure refers to thespatial peak temporal average intensity (ISPTA).

The use of intensity, however, as an indicator ofsafety is limited, particularly where Doppler is con-cerned, as Doppler intensities can be considerablygreater than those in B-mode imaging. The Foodand Drug Administration (FDA) sets maximumintensity levels allowed for machine output, whichdiffer according to the application.9

Biological effects of ultrasound

Harmful effects from ultrasound have been docu-mented in laboratory conditions. These includethermal effects and mechanical effects.


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Thermal effects are demonstrated as a slightrise in temperature, particularly in close proximityto the transducer face, during ultrasound scanning.This local effect is usually of no significance but theoperator must be aware of the phenomenon. Themost significant thermal effects occur at bone/tis-sue interfaces and are greater with pulsed Doppler.Increases in temperature of up to 5˚C have beenproduced. Areas at particular risk are fetal bonesand the interfaces in transcranial Doppler ultra-sound scans.

Pulsed Doppler has a greater potential for heat-ing than B-mode imaging as it involves greatertemporal average intensities due to high pulse rep-etition frequency (PRF) and because the beam isfrequently held stationary over an area whileobtaining the waveform. Colour and powerDoppler usually involve a greater degree of scan-ning and transducer movement, which involves apotentially lower heating potential than withpulsed Doppler. Care must be taken to limit theuse of pulsed Doppler and not to hold the trans-ducer stationary over one area for too long.

Mechanical effects, which include cavitationand radiation pressure, are caused by stresses in thetissues and depend on the amplitude of the ultra-sound pulse. These effects are greatest around gas-filled organs, such as lungs or bowel and have, inlaboratory conditions, caused small surface bloodvessels in the lungs to rupture. Potentially, theseeffects could be a hazard when using contrastagents which contain microbubbles.

Safety indices (thermal and mechanical indices)

In order to inform users about the machine condi-tions which may potentially be harmful, mechani-cal and thermal indices are now displayed as anoutput display standard (ODS) on all equipmentmanufactured after 1998. This makes operatorsaware of the ultrasound conditions which mayexceed the limits of safety and enables them to takeavoiding action, such as reducing the power orrestricting the scanning time in that area.

In simple terms the mechanical index (MI) isrelated to amplitude and indicates how ‘big’ anultrasound pulse is, giving an indication of thechances of mechanical effects occurring. It is there-fore particularly relevant in the abdomen when

scanning gas-filled bowel or when using micro-bubble contrast agents. Gas bodies introducedby contrast agents increase the probablility ofcavitation.

The thermal index (TI) gives an indication ofthe temperature rise which might occur within theultrasound beam, aiming to give an estimate ofthe reasonable worst-case temperature rise. The TIcalculation alters, depending upon the application,giving rise to three indices: the soft-tissue thermalindex (TIS), the bone-at-focus index (TIB) andthe bone-at-surface, or cranial index (TIC). Thefirst of these is obviously most relevant for abdom-inal applications. In well-perfused tissue, such asthe liver and spleen, thermal effects are less likelydue to the cooling effect of the blood flow.

The display of safety indices is only a generalindication of the possibility of biological hazardsand cannot be translated directly into real heatingor cavitation potential.10 These ‘safety indices’ arelimited in several ways. They require the user tobe educated with respect to the implications of thevalues shown and they do not take account ofthe duration of exposure, which is particularlyimportant in assessing the risk of thermal damage.4In addition, the TI does not take account of thepatient’s temperature, and it is logical to assumethat increased caution is therefore required in scan-ning the febrile patient.

MI and TI are also unlikely to portray the opti-mum safety information during the use of contrastagents, in which, theoretically, heating effects andcavitation may be enhanced.5

Other hazards

Whilst most attention in the literature is focusedon the possible biological effects of ultrasound,there are several other safety issues which arewithin the control of the operator.

Electrical safety All ultrasound machinesshould be subject to regular quality controland should be regularly checked for any signs ofelectrical hazards. Loose or damaged wiring, forexample, is a common problem if machines areroutinely used for mobile work. Visible damage toa transducer, such as a crack in the casing, shouldprompt its immediate withdrawal from serviceuntil a repair or replacement is effected.


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Microbiological safety It is the responsibilityof the sonographer to minimize the risks of cross-infection. Most manufacturers make recommenda-tions regarding appropriate cleaning agents fortransducers, which should be carefully followed.Sterile probe covers should be used in cases wherethere is an increased risk of infection.

Operator safety By far the most serious haz-ard of all is that of the untrained or badly trainedoperator. Misdiagnosis is a serious risk for thosenot aware of the pitfalls. Apart from the implica-tions for the patient of subsequent incorrect man-agement, the operator risks litigation which isdifficult or impossible to defend if they have hadinadequate training in ultrasound.

Work-related musculoskeletal disorders

There is increasing concern about WRMSD relatedto ultrasound scanning, as workloads increase and ithas been estimated that a significant proportion ofsonographers who practise full-time ultrasoundscanning may be affected.2 One contributing factoris the ergonomic design of the ultrasound machines,together with the position adopted by the operatorduring scanning. While more attention is now beingpaid by ultrasound manufacturers to designs whichlimit WRMSD, there are various other contributingfactors which should be taken into account whenproviding ultrasound services. Well-designed,adjustable seating for operators, adjustable patientcouches, proper staff training for manoeuvringpatients and a varied work load all contribute tominimizing the potential problems to staff.

Hand-held, portable ultrasound machines arenow available. Provided they are of sufficient func-tionality to provide the service required, they mayalso potentially limit the problems encounteredwhen manoeuvring larger scanners around hospitalwards and departments.

The safe practice of ultrasound

It is fair to say that the safety of ultrasound is lessof an issue in abdominal scanning than in obstetricor reproductive organ scanning. Nevertheless it isstill incumbent upon the operator to minimize theultrasound dose to the patient in any practicableway.

The use of X-rays is governed by the ALARAprinciple—that of keeping the radiation dose AsLow As Reasonably Achievable. Although the risksassociated with radiation are not present in the useof ultrasound, the general principle of keeping theacoustic exposure as low as possible is still goodpractice and many people still refer to ALARA inthe context of diagnostic ultrasound (see Box 1.3).

MEDICOLEGAL ISSUES

Litigation in medical practice is increasing and thefield of ultrasound is no exception to this.Although currently the majority of cases involvefirstly obstetric and secondly gynaecological ultra-sound, it is prudent for the operator to be aware ofthe need to minimize the risks of successful litiga-tion in all types of scanning procedures.

Patients have higher expectations of medicalcare than ever before and ultrasound practitionersshould be aware of the ways in which they can pro-tect themselves should a case go to court. The


Box 1.3 Steps for minimizing the ultrasounddose

● Ensure operators are properly trained, prefer-ably on recognized training programmes.

● Minimize the output (or power) level. Useamplification of the received echoes to manip-ulate the image in preference to increasing thetransmitted power.

● Minimize the time taken to perform the exam.● Don’t rest the transducer on the skin surface

when not scanning.● Make sure the clinical indications for the scan

are satisfactory and that a proper request hasbeen received. Don’t do unnecessary ultra-sound examinations.

● Be aware of the safety indices displayed on theultrasound machine. Limit the use of pulsedDoppler to that necessary to contribute to thediagnosis.

● Make the best use of your equipment—maxi-mize the diagnostic information by manipulat-ing the controls effectively.

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onus is upon the defendant to prove that he or sheacted responsibly and there are several helpfulguidelines which should routinely be followed (seeBox 1.4).11

The medicolegal issues surrounding ultrasoundmay be different according to whether the opera-tor is medically or non-medically qualified.Depending on their profession, operators are con-strained by codes of conduct of their respectivecolleges and/or Councils.12 Either way, the opera-tor is legally accountable for his or her professionalactions.

If non-medically qualified personnel are to per-form and report on scans (as happens in the UK,USA and Australia), this task must be properly del-egated by a medically qualified practitioner, forexample a radiologist in the case of abdominalscanning. As the role of sonographers continues toexpand, it is noteworthy that the same standard ofcare is expected from medically and non-medicallyqualified staff alike.13 To avoid liability, practition-ers must comply with the Bolam test, in which theyshould be seen to be acting in accordance withpractice accepted as proper by a responsible bodyof relevant medical people.

DEPARTMENTAL GUIDELINES/SCHEMESOF WORK

It is generally considered good and safe practice touse written guidelines for ultrasound examinations.3

These serve several purposes:

● They may be used to support a defence againstlitigation (provided, of course, that theoperator can prove he or she has followed suchguidelines).

● They serve to impose and maintain a minimumstandard, especially within departments whichmay have numerous operators of differingexperience levels.

● They serve to inform operators of currentpractice.

Guidelines should ideally be:

● Written by, and have input from, thosepractising ultrasound in the department(usually a combination of medically and non-medically qualified personnel), taking intoaccount the requirements of referringclinicians, available equipment and other localoperational issues.

● Regularly reviewed and updated to takeaccount of the latest literature and practices.

● Flexible, to allow the operator to tailor thescan to the patient’s clinical presentation andindividual requirements.

Guidelines which are too prescriptive anddetailed are likely to be ignored by operators asimpractical. The guidelines should be broadenough to allow operators to respond to differentclinical situations in an appropriate way whileensuring that the highest possible standard of scanis always performed. In cases when it is simply notpossible to adhere to departmental guidelines, thereasons should be stated on the report, for exam-ple when the pancreas cannot be demonstrated dueto body habitus or overlying bowel gas.

QUALITY ASSURANCE

The principles of quality assurance affect variousaspects of the ultrasound service offered. These


Box 1.4 Guidelines for defensive scanning(adapted from Meire HB11)

● Ensure you are properly trained. Operatorswho have undergone approved training areless likely to make mistakes.

● Act with professionalism and courtesy. Goodcommunication skills go a long way to avoid-ing litigation.

● Use written guidelines or schemes of work.● Ensure a proper request for the examination

has been received.● A written report should be issued by the oper-

ator.● Record images to support your findings.● Clearly state any limitations of the scan which

may affect the ability to make a diagnosis.● Make sure that the equipment you use is ade-

quate for the job.

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include staff issues (such as education and training,performance and continuing professional develop-ment), patient care, the work environment (includ-ing health and safety issues) and quality assuranceof equipment. Quality assurance checks on ultra-sound equipment, unlike most other aspects of anultrasound service, involve measurable and repro-ducible parameters.

Equipment tests

After installation, a full range of equipment testsand safety checks should be carried out and theresults recorded. This establishes a baseline per-formance against which comparisons may later bemade. These tests should normally be carried outby qualified medical physicists.

It is useful to take a hard-copy image of a tissue-mimicking phantom, with the relevant settingsmarked on it. These images form a reference againstwhich the machine’s subsequent performance canbe assessed. If your machine seems to be perform-ing poorly, or the image seems to have deterioratedin some way, you will have the proof you require.

A subsequent, regular testing regime must thenbe set up, to ensure the standards of quality and

safety are maintained. This programme can be setup in conjunction with the operators and the med-ical physics department and relevant recordsshould be kept. The use of a tissue-mimickingphantom enables the sonographer to perform cer-tain tests in a reproducible and recordable manner(Fig. 1.12).

Checks should be carried out for all probes onthe machine.

Suggested equipment checks include:

● caliper accuracy● system sensitivity and penetration● axial and lateral resolution● slice thickness● grey scale● dead zone● checks on the various machine controls/func-

tions● output power● safety checks: electrical, mechanical, biological

and thermal, including a visual inspection of allprobes and leads

● imaging device checks for image quality, set-tings, dynamic range, functionality and electri-cal safety


A B

Figure 1.12 Tissue-mimicking phantom. (A) When using a high-frequency linear array, cross-sections of the wires inthe phantom are clearly demonstrated as small dots. (B) When using a curved array of a lower frequency, such as thatused for abdominal scanning, the lateral resolution is seen to deteriorate in the far field as the beam diverges. Thewires are displayed correctly in the near field but appear as short lines in the far field. Spacing of the wires is known,allowing caliper accuracy to be assessed.

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● biopsy guide checks● colour, power and spectral Doppler checks

(complex, requiring specialized equipment).

Some of these checks can be easily and quickly car-ried out by users in the department on a regular

basis, for example caliper checks and biopsy guidechecks. Others are more complex and may beappropriately undertaken by specialist medicalphysicists. All equipment should undergo regularservicing and any interim faults should naturally bereported.


References1. Desser TS, Jedrzejewicz MS, Bradley C. 2000 Native

tissue harmonic imaging: basic principles and clinicalapplications. Ultrasound Quarterly 16, no. 1: 40–48.

2. Society of Radiographers. 2002 The Causes ofMuskuloskeletal Injury Amongst Sonographers in theUK. SoR, London.

3. UK Association of Sonographers. 1996 Guidelines forProfessional Working Practice. UKAS, London.

4. British Medical Ultrasound Society. 2000 Guidelinesfor the acquisition and retention of hard copyultrasound images. BMUS Bulletin 8: 2.

5. ter Haar G, Duck FA (eds). 2000 The Safe Use ofUltrasound in Medical Diagnosis. BMUS/BIR,London.

6. European Federation of Societies for Ultrasound inMedicine and Biology. 1996 Clinical safety statementfor diagnostic ultrasound. EFSUMB Newsletter 10: 2.

7. World Federation for Ultrasound in Medicine andBiology. 1998 Symposium on safety of ultrasound inmedicine: conclusions and recommendations onthermal and non-thermal mechanisms for biologicaleffects of ultrasound. Ultrasound in Medicine andBiology 24: 1–55.

8. American Institute for Ultrasound in Medicine. 1988Bioeffects and considerations for the safety ofdiagnostic ultrasound. Journal of Ultrasound inMedicine 7: Suppl.

9. Food and Drug Administration: US Department ofHealth and Human Services. 1997 Information forManufacturers Seeking Marketing Clearance ofDiagnostic Ultrasound Systems and Transducers.Center for Devices and Radiological Health Rockville,MD.

10. Duck FA. 1997 The meaning of thermal index (TI)and mechanical index (MI) values. BMUS Bulletin5: 36–40.

11. Meire HB. 1996 Editorial. Ultrasound-relatedlitigation in obstetrics and gynecology: the need fordefensive scanning. Ultrasound in Obstetrics andGynecology 7: 233–235.

12. Council for Professions Supplementary to Medicine.1995 Statement of Conduct/Code of Practice.Radiographer’s Board, London.

13. Dimond B. 2000 Red dots and radiographers’liability. Health care risk report, October. ClinicalNegligence 10–13.

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INTRODUCTION

Ultrasound is the dominant first-line investigationfor an enormous variety of abdominal symptomsbecause of its non-invasive and comparativelyaccessible nature. Its success, however, in terms ofa diagnosis, depends upon numerous factors, themost important of which is the skill of the operator.

Because of their complexity and extent, the nor-mal appearances and haemodynamics of the hepato-biliary system are dealt with in this chapter, togetherwith some general upper-abdominal scanning issues.The normal appearances of the other abdominalorgans are included in subsequent relevant chapters.

It is good practice, particularly on the patient’sfirst attendance, to scan the whole of the upperabdomen, focusing particularly on the relevantareas, but also excluding or identifying any othersignificant pathology. A full abdominal surveywould normally include the liver, gallbladder, bil-iary tree, pancreas, spleen, kidneys and retroperi-toneal structures. Apart from the fact that manypathological processes can affect multiple organs, anumber of significant (but clinically occult) patho-logical processes are discovered incidentally, forexample renal carcinoma or aortic aneurysm. Athorough knowledge of anatomy is assumed at thisstage, but diagrams of upper abdominal sectionalanatomy are included in the appendix to this chap-ter for quick reference (see pp. 36–39).

It is important always to remember the opera-tor-dependent nature of ultrasound scanning (seeChapter 1); although the dynamic nature of thescan is a huge advantage over other forms of

Chapter 2

The normal hepatobiliary system

17

CHAPTER CONTENTS

Introduction 17General pointers on upper-abdominal

technique 18The liver 18

Normal appearance 18The segments of the liver 24Hepatic vasculature 25Haemodynamics of the liver 25

The gallbladder 27Normal variants of the gallbladder 29Pitfalls in scanning the gallbladder 29

Bile ducts 31Bile duct measurements 33Techniques 33

Some common referral patterns forhepatobiliary ultrasound 33Jaundice 34Abnormal liver function tests 35Other common reasons for referral 35

Appendix: Upper-abdominal anatomy 36

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imaging, the operator must continuously adjusttechnique to obtain the maximum diagnosticinformation. In any abdominal ultrasound surveythe operator assesses the limitations of the scan andthe level of confidence with which pathology canbe excluded or confirmed. The confidence limitshelp in determining the subsequent investigationsand management of the patient.

It is important, too, to retain an open mindabout the diagnosis when embarking on the scan;an operator who decides the likely diagnosis on aclinical basis may sometimes be correct but, in try-ing to fit the scan to match the symptoms, risksmissing significant pathology.

GENERAL POINTERS ON UPPER-ABDOMINAL TECHNIQUE

Scanning technique is not something that can belearnt from a book. There is absolutely no substi-tute for regular practical experience under thesupervision of a qualified ultrasound practitioner.

There are, however, some general approacheswhich help to get the best from the scanningprocedure:

● Scan in a systematic way to ensure the whole ofthe upper abdomen has been thoroughlyinterrogated. The use of a worksheet, whichindicates the structures to be examined, isadvisable when learning.1

● Always scan any organ in at least two planes,preferably at right angles to each other. Thisreduces the risk of missing pathology and helpsto differentiate artefact from true pathology.

● Where possible, scan in at least two patientpositions. It is surprising how the availableultrasound information can be enhanced byturning your patient oblique, decubitus or erect.Inaccessible organs flop into better view andbowel moves away from the area of interest.

● Use a combination of sub- and intercostalscanning for all upper-abdominal scanning. Thedifferent angles of insonation can revealpathology and eliminate artefact.

● Don’t limit yourself to longitudinal andtransverse sections. Use a variety of planes and

angulations. Trace ducts and vessels along theircourses. Use the transducer like a pair of eyes.

● Deep inspiration is useful in a proportion ofpatients, but not all. Sometimes it can makematters worse by filling the stomach with airand obscuring large areas. An intercostalapproach with the patient breathing gentlyoften has far more success.

● Positioning patients supine, particularly ifelderly or very ill, can make them breathlessand uncomfortable. Raise the patient’s head asmuch as necessary; a comfortable patient ismuch easier to scan.

● Images are a useful record of the scan and howit has been performed, but don’t make theseyour primary task. Scan first, sweepingsmoothly from one aspect of the organ to theother in two planes, then take the relevantimages to support your findings.

● Make the most of your equipment (seeChapter 1). Increase the confidence level ofyour scan by fully utilizing all the availablefacilities, using Doppler, tissue harmonics,changing transducers and frequencies andmanipulating the machine settings andprocessing options.

THE LIVER

Normal appearanceThe liver is a homogeneous, mid-grey organ onultrasound. It has the same, or slightly increasedechogenicity when compared to the cortex of theright kidney. Its outline is smooth, the inferiormargin coming to a point anteriorly (Fig. 2.1).The liver is surrounded by a thin, hyperechoic cap-sule, which is difficult to see on ultrasound unlessoutlined by fluid (Fig. 2.2).

The smooth parenchyma is interrupted by ves-sels (see below) and ligaments (Figs 2.3–2.15) andthe liver itself provides an excellent acoustic win-dow on to the various organs and great vessels sit-uated in the upper abdomen.

The ligaments are hyperechoic, linear structures;the falciform ligament, which separates theanatomical left and right lobes is situated at the


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superior margin of the liver and is best demon-strated when surrounded by ascitic fluid. It sur-rounds the left main portal vein and is known asthe ligamentum teres as it descends towards theinfero-anterior aspect of the liver (Figs 2.9 and2.15). The ligamentum venosum separates thecaudate lobe from the rest of the liver (Fig. 2.6).

The size of the liver is difficult to quantify, asthere is such a large variation in shape betweennormal subjects and direct measurements are noto-riously inaccurate. Size is therefore usually assessedsubjectively. Look particularly at the inferior mar-gin of the right lobe which should come to a pointanterior to the lower pole of the right kidney (Fig.2.1). A relatively common variant of this is theReidel’s lobe, an inferior elongation of segment VI

on the right. This is an extension of the right lobeover the lower pole of the kidney, with a roundedmargin (Fig. 2.16), and is worth remembering as apossible cause of a palpable right upper quadrant‘mass’.

To distinguish mild enlargement from a Reidel’slobe, look at the left lobe. If this also looks bulky,with a rounded inferior edge, the liver is enlarged.A Reidel’s lobe is usually accompanied by a smaller,less accessible left lobe.

THE NORMAL HEPATOBILIARY SYSTEM 19

Figure 2.1 Longitudinal section (LS) through the rightlobe of the liver. The renal cortex is slightly lessechogenic than the liver parenchyma. LIVER

Figure 2.2 The capsule of the liver (arrows) isdemonstrated with a high-frequency (7.5 MHz) probe.

Right lobe of liver

Branch of RPV

Branch of RHV

Right kidney

Quadratus lumborum

Diaphragm

A B

Morrison’s pouch

Figure 2.3 LS through the right lobe of the liver and right kidney. RPV = right portal vein; RHV = right hepatic vein.

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Right lobe of liver

Right adrenal

Medial aspectright kidney

Diaphragmatic crusA B

Figure 2.4 LS, right lobe, just medial to the right kidney.

Right lobe of liver

RPV

IVC

RRA

Crus

A B

Figure 2.5 LS, right lobe, angled medially towards the inferior vena cava (IVC). RRA = right renal artery.

Left lobe of liver

LPV

Stomach

HA

Head of pancreas

Splenic vein

IVC

Ligamentumvenosum

Caudate lobeA B

Figure 2.6 LS, midline, through the left lobe, angled right towards the IVC. LPV = left portal vein; HA = hepaticartery.

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Left lobe of liver

Stomach

SA

Coeliac axis

Oesophagus

Aorta

A B

Body of pancreas

SV

SMA

Figure 2.7 LS through the midline. SV = splenic vein; SA = splenic artery; SMA = superior mesenteric artery.

Left lobe of liver

Stomach

Body of pancreas

SV

SMA

Aorta

Coeliac axis

A B

Figure 2.8 LS just to the left of midline.

Ligamentumteres

Stomach

Shadowingfromligament

LPV

Left lobe of liver

A B

Figure 2.9 LS, left lobe of liver.

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Branch of RPV

IVC

Crus

Right lobe of liver

A B

Figure 2.10 Transverse section (TS) through the liver, above the confluence of the hepatic veins.

LHV

IVC

MHV

RHV

BA

Figure 2.11 TS at the confluence of the hepatic veins (HV).

Left lobe of liver

PV

IVC

Right lobe of liver

Caudate lobe

A BFigure 2.12 TS at the porta hepatis. PV = portal vein.

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Gallbladder

Shadowingfrom bowel

Inferior aspectright lobe of liver

Right kidney

A B

Figure 2.13 TS through the right kidney.

Left lobe ofliver

SV

Aorta

Head ofpancreas

CBD

IVC

SMA

Tail ofpancreas

A B

Figure 2.14 TS at the epigastrium. CBD = common bile duct.

Inferior aspectleft lobe of liver

Ligamentumteres

Stomach

A B

Figure 2.15 TS at the inferior edge of the left lobe.

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The segments of the liverIt is often sufficient to talk about the ‘right’ or‘left’ lobes of the liver for the purposes of manydiagnoses. However, when a focal lesion is identi-fied, especially if it may be malignant, it is usefulto locate it precisely in terms of the surgical seg-

ments. This allows subsequent correlation withother imaging, such as computerized tomography(CT) or magnetic resonance imaging (MRI), andis invaluable in planning surgical procedures.

The segmental anatomy system, proposed byCouinaud in 1954,2 divides the liver into eightsegments, numbered in a clockwise direction.They are divided by the portal and hepatic veinsand the system is used by surgeons today whenplanning surgical procedures (Fig. 2.17). This sys-tem is also used when localizing lesions with CTand MRI.

Identifying the different segments on ultrasoundrequires the operator to form a mental three-dimensional image of the liver. The dynamic natureof ultrasound, together with the variation in planesof scan, makes this more difficult to do than for CTor MRI. However, segmental localization ofhepatic lesions by an experienced operator can be asaccurate with ultrasound as with MRI.3 Systematicscanning through the liver, in transverse section,identifies the main landmarks of the hepatic veins(Fig. 2.11) separating segments VII, VIII, IV andII in the superior part of the liver. As the transduceris moved inferiorly, the portal vein appears, andbelow this segments V and VI are located.


Figure 2.16 LS through the right lobe, demonstrating aReidel’s lobe extending below the right kidney. (Comparewith the normal liver in Figure 2.1.)

Middle hepatic vein

I

IV

V

VI

VII

VIII

II

III

Right hepatic vein

Left hepatic vein

Falciform ligament

Portal veinFigure 2.17 The surgicalsegments of the liver (afterCouinaud2).

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Hepatic vasculatureThe portal veins radiate from the porta hepatis,where the main portal vein (MPV) enters the liver(Fig. 2.18). They are encased by the hyperechoic,fibrous walls of the portal tracts, which make themstand out from the rest of the parenchyma. Alsocontained in the portal tracts are a branch of thehepatic artery and a biliary duct radical. These lat-ter vessels are too small to detect by ultrasound inthe peripheral parts of the liver, but can readily bedemonstrated in the larger, proximal branches(Fig. 2.19).

At the porta, the hepatic artery generally crossesthe anterior aspect of the portal vein, with thecommon duct anterior to this (Fig. 2.20). In acommon variation the artery lies anterior to theduct. Peripherally, the relationship between thevessels in the portal tracts is variable, (Fig. 2.21).

The three main hepatic veins, left, middle andright, can be traced into the inferior vena cava(IVC) at the superior margin of the liver (Fig.2.11). Their course runs, therefore, approximatelyperpendicular to the portal vessels, so a section ofliver with a longitudinal image of a hepatic vein islikely to contain a transverse section through a por-tal vein, and vice versa.

Unlike the portal tracts, the hepatic veins do nothave a fibrous sheath and their walls are thereforeless reflective. Maximum reflectivity of the vessel

walls occurs with the beam perpendicular(Fig. 2.22).

The anatomy of the hepatic venous confluencevaries. In most cases the single, main right hepaticvein (RHV) flows directly into the IVC, and themiddle and left have a common trunk. In 15–35%of patients the left hepatic vein (LHV) and middlehepatic vein (MHV) are separate. This usually hasno significance to the operator. However, it may bea significant factor in planning and performinghepatic surgery, especially tumour resection, as thesurgeon attempts to retain as much viable hepatictissue as possible with intact venous outflow(Fig. 2.23).4

Haemodynamics of the liverPulsed and colour Doppler to investigate thehepatic vasculature are now established aids todiagnosis in the upper abdomen. Doppler shouldalways be used in conjunction with the real-timeimage and in the context of the patient’s present-ing symptoms. Used in isolation it can be highlymisleading. Familiarity with the normal Doppler


r

l

Figure 2.18 The right and left branches of the portalvein.

Figure 2.19 The portal vein radical is associated with abranch of the hepatic artery and a biliary duct (arrows)within the hyperechoic fibrous sheath.

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spectra is an integral part of the upper-abdominalultrasound scan.

Doppler of the portal venous and hepatic vascularsystems gives information on the patency, velocityand direction of flow. The appearance of the variousspectral waveforms relates to the downstream resist-ance of the vascular bed (see Chapter 1).

The portal venous system

Colour Doppler is used to identify blood flow inthe splenic and portal veins (Figs 2.24 and 2.25).

The direction of flow is normally hepatopetal, thatis towards the liver. The main, right and left portalbranches can best be imaged by using a rightoblique approach through the ribs, so that thecourse of the vessel is roughly towards the trans-ducer, maintaining a low (< 60˚) angle with thebeam for the best Doppler signal.

The normal portal vein diameter is highly vari-able but does not usually exceed 16 mm in a rest-ing state on quiet respiration.5 The diameterincreases with deep inspiration and also in responseto food and to posture changes. An increaseddiameter may also be associated with portal hyper-tension in chronic liver disease (see Chapter 4). Anabsence of postprandial increase in diameter is alsoa sign of portal hypertension.

The normal portal vein (PV) waveform ismonophasic (Fig. 2.26) with gentle undulationswhich are due to respiratory modulation and car-diac activity. This characteristic is a sign of the nor-mal, flexible nature of the liver and may be lost insome fibrotic diseases.

The mean PV velocity is normally between 12and 20 cm per second6 but the normal range iswide. (A low velocity is associated with portal hyper-tension. High velocities are unusual, but can be dueto anastomotic stenoses in transplant patients.)

The hepatic veins

The hepatic veins drain the liver into the IVC,which leads into the right atrium. Two factorsshape the hepatic venous spectrum: the flexiblenature of the normal liver, which can easily expandto accommodate blood flow, and the close prox-imity of the right atrium, which causes a brief ‘kick’of blood back into the liver during atrial systole(Fig. 2.27). This causes the spectrum to be tripha-sic. The veins can be seen on colour Doppler to bepredominantly blue with a brief red flash duringatrial contraction. Various factors cause alterationsto this waveform: heart conditions, liver diseasesand extrahepatic conditions which compress theliver, such as ascites. Abnormalities of the hepaticvein waveform are therefore highly unspecific andshould be taken in context with the clinical picture.

As you might expect, the pulsatile nature of thespectrum decreases towards the periphery of theliver, remote from the IVC.


A

B

HA

HA

CDPV

CD

Figure 2.20 (A) The porta hepatis. (B) A variant with thehepatic artery anterior to the duct. CD = common duct.

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The hepatic artery

The main hepatic artery arises from the coeliac axisand carries oxygenated blood to the liver from theaorta. Its origin makes it a pulsatile vessel and therelatively low resistance of the hepatic vascular bedmeans that there is continuous forward flowthroughout the cardiac cycle (Fig. 2.28). In a nor-mal subject the hepatic artery may be elusive oncolour Doppler due to its small diameter and tortu-ous course. Use the MPV as a marker, scanning

from the right intercostal space to maintain a lowangle with the vessel. The hepatic artery is just ante-rior to this and of a higher velocity (that is, it has apaler colour of red on the colour map (Fig. 2.24)).

THE GALLBLADDER

The normal gallbladder is best visualized after fasting,to distend it. It should have a hyperechoic, thin walland contain anechoic bile (Fig. 2.29). Measure thewall thickness in a longitudinal section of the gall-bladder, with the calipers perpendicular to the wallitself. (A transverse section may not be perpendicularto the wall, and can overestimate the thickness.)

After fasting for around six hours, it should be dis-tended with bile into an elongated pear-shaped sac.The size is too variable to allow direct measurementsto be of any use, but a tense, rounded shape can indi-cate pathological, rather than physiological dilatation.

Because the size, shape and position of the gall-bladder are infinitely variable, so are the techniquesrequired to scan it. There are, however, a numberof useful pointers to maximize visualization of thegallbladder:

● Use the highest frequency possible: 5.0 MHz orhigher is especially useful for anterior gallbladders.

● Use a high line density to pick up tiny stonesor polyps (reduce the sector angle and theframe rate if possible). Make sure the focal


A BFigure 2.21 The relationship of the biliary duct to the portal vein varies as the vessels become more peripheral. In (A)the duct lies anterior to the LPV; in (B) the duct is posterior to the LPV.

Figure 2.22 The left hepatic vein. Vessel walls are notas reflective as portal veins; however, maximumreflectivity is produced when the beam is perpendicularto the walls, as at the periphery of this vessel.

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zone is set over the back wall of the gallbladderto maximize the chances of identifying smallstones (see Chapters 1 and 3).

● Alter the time gain compensation (TGC) toeliminate or minimize anterior artefacts and

reverberation echoes inside the gallbladder,particularly in the near field.

● Use tissue harmonic imaging to reduce artifactwithin the gallbladder and sharpen the imageof the wall (particularly in a large abdomen).

● Always scan the gallbladder in at least twoplanes (find the gallbladder’s long axis,incorporating the neck and fundus; sweep fromside to side, then transversely from neck tofundus) and two patient positions. You willalmost certainly miss pathology if you do not.


RHV MHVLHV

IVC

BA

Inferior RHV

Middle RHV

Figure 2.23 (A) Configuration of the hepatic venous system. (B) Inferior middle hepatic vein (arrow) arising from theIVC.

Figure 2.24 Main portal vein at the porta hepatisdemonstrating hepatopetal flow. The higher velocityhepatic artery lies adjacent to the Main portal vein (arrow).

Figure 2.25 TS through the epigastrium, demonstratingthe normal splenic vein with flow towards the liver. Notethe change from red to blue as the vessel curves awayfrom the transducer.

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● The gallbladder may be ‘folded’ (the so-calledPhrygian cap). To interrogate its contents fully,unfold it by turning the patient decubitus (rightside raised), almost prone or erect (Fig. 2.30).

● Bowel gas over the fundus can also be movedby various patient positions.

Normal variants of the gallbladderThe mesenteric attachment of the gallbladder tothe inferior surface of the liver is variable in length.This gives rise to large variations in position; at oneend of the spectrum the gallbladder, attached onlyat the neck, may be fairly remote from the liver,even lying in the pelvis; at the other the gallblad-der fossa deeply invaginates the liver and the gall-bladder appears to lie ‘intrahepatically’ enclosed onall sides by liver tissue.

The presence of a true septum in the gallbladderis rare. A folded gallbladder frequently gives theimpression of a septum but this can be distin-guished by positioning the patient to unfold thegallbladder.

Occasionally a gallbladder septum completelydivides the lumen into two parts. True gallbladderduplication is a rare entity (Fig. 2.31) and it isimportant not to mistake this for a gallbladder witha pericholecystic collection in a symptomatic

patient. Occasionally the gallbladder is absent alto-gether.

Pitfalls in scanning the gallbladderIf the gallbladder cannot be found● Check for previous surgery; a cholecystectomy

scar is usually obvious, but evidence oflaparoscopic surgery may be difficult to see inthe darkened scanning room.

● Check the patient has fasted.


Figure 2.26 Normal portal vein waveform. Respiratorymodulations are evident.

A

RM L

B

Figure 2.27 (A) The confluence of the right, middle andleft hepatic veins with the IVC. (B) Normal hepatic venouswaveform. The reverse flow in the vein (arrows) is due toatrial systole. Note that the image has also been frozenduring atrial systole, as the hepatic vein appears red.

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● Look for an ectopic gallbladder, for examplepositioned low in the pelvis.

● Check that a near-field artefact has notobscured an anterior gallbladder, a particularproblem in very thin patients.

● Ensure the scanner frequency and settings areoptimized, find the porta hepatis and scan justbelow it in transverse section. This is the areaof the gallbladder fossa and you should see atleast the anterior gallbladder wall if thegallbladder is present (Fig. 2.32).

● A contracted, stone-filled gallbladder, producingheavy shadowing, can be difficult to identify dueto the lack of any contrasting fluid in the lumen.

Duodenum mimicking gallbladder pathology● The close proximity of the duodenum to the

posterior gallbladder wall often causes it toinvaginate the gallbladder. Maximize your machinesettings to visualize the posterior gallbladder wallseparate from the duodenum and turn the patientto cause the duodenal contents to move.

● Other segments of fluid-containinggastrointestinal tract can also cause confusion(Fig. 2.33).

Stones that don’t shadow● Ensure they are stones and not polyps by

standing the patient erect and watching them

move with gravity. (Beware—polyps on longstalks also move around.)

● The stones may be smaller than the beamwidth, making the shadow difficult to display.Make sure the focal zone is set at the back ofthe gallbladder.

● Increase the line density, if possible, byreducing the field of view.

● Scan with the highest possible frequency toensure the narrowest beam width.

● Reduce the TGC and/or power to make sureyou have not saturated the echoes distal to thegallbladder (see Chapter 3).

Beware the folded gallbladder● You may miss pathology if the gallbladder is

folded and the fundus lies underneath bowel.Always try to unfold it by positioning thepatient (Fig. 2.30).

● A fold in the gallbladder may mimic a septum.Septa are comparatively rare and have beenover-reported in the past due to the presenceof folding.

Pathology or artefact?

Sometimes the gallbladder may contain someechoes of doubtful significance, or be insufficientlydistended to evaluate accurately. A rescan, after ameal followed by further fasting, can be useful.


A B C

Figure 2.28 (A) The hepatic artery may be difficult to locate with colour Doppler in some subjects. (B) The same patientusing power Doppler; visualization is improved. (C) The normal hepatic artery waveform demonstrates a relatively high-velocity systolic peak (arrowhead) with good forward end-diastolic flow (arrow).

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This can flush out sludge, redistending the gall-bladder with clear bile. It may also help to clarifyany confusing appearances of adjacent bowel loops.

BILE DUCTS

The common duct can be easily demonstrated in itsintrahepatic portion just anterior and slightly to theright of the portal vein. A cross-section of the mainhepatic artery can usually be seen passing between


A

B

C

Figure 2.29 The gallbladder: (A) LS, (B) TS. (C) Falseappearance of wall thickening is produced (arrow) whenthe angle of scan is not perpendicular to the gallbladderwall in TS.

A

B

Figure 2.30 (A) A folded gallbladder is difficult toexamine with the patient supine. (B) Turning the patientdecubitus, right side raised, unfolds the gallbladder,enabling the lumen to be satisfactorily examined.

Figure 2.31 Double gallbladder—an incidental findingin a young woman.

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the vein and the duct (Figs 2.20A and 2.34), althougha small proportion of hepatic arteries lie anterior tothe duct (Fig. 2.20B). At this point it is usuallyreferred to as the common duct, although it may, infact, represent the right hepatic duct7 rather than

the common bile duct, because we can’t tell at whatpoint it is joined by the cystic duct.

The extrahepatic portion of the duct is less easyto see as it is often obscured by overlying duodenalgas. Good visualization of the duct usually requiresperseverance on the part of the operator. It is insuf-ficient just to visualize the intrahepatic portion ofthe duct, as early obstruction may be present witha normal-calibre intrahepatic duct and dilatation ofthe distal end. (Fig. 2.35).


Figure 2.32 A contracted, thick-walled gallbladderlocated in the gallbladder fossa on TS.

A

B

Figure 2.33 (A) The duodenum frequently invaginatesthe posterior wall of the gallbladder and may mimicpathology if the machine settings are not correctlymanipulated. (B) Fluid-filled stomach near thegallbladder fossa mimics a gallbladder containing astone. The real gallbladder was normal.

Figure 2.34 CBD at the porta hepatis. The lower end isfrequently obscured by shadowing from the duodenum.The duct should be measured at its widest portion.

Figure 2.35 Visualization of the lower end of the ductoften requires the operator to persevere with techniqueand patient positioning. The normal duct (calipers) isseen in the head of the pancreas.

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Bile duct measurementsThe internal diameter of the common duct is usu-ally taken as 6 mm or less. It is age-dependent,however, and can be 8 or 9 mm in an elderly per-son, due to degeneration of the elastic fibre in theduct wall. Ensure this is not early obstruction bythoroughly examining the distal common bileduct or rescanning after a short time interval. Thediameter can vary quite considerably, not onlybetween subjects, but along an individual duct.The greatest measurement should be recorded, inlongitudinal section. Never measure the duct in atransverse section (for example at the head of pan-creas); it is invariably an oblique plane throughthe duct, which will overestimate the diameter.Intrahepatically, the duct diameter decreases. Theright and left hepatic ducts are just visible, butmore peripheral branches are usually too smallto see.

Patients with a cholecystectomy who have hadprevious duct dilatation frequently also have a per-sistently dilated, but non-obstructed, duct (Fig.2.36). Be suspicious of a diameter of 10 mm ormore as this is associated with obstruction due toformation of stones in the duct.

TechniquesThe main, right and left hepatic ducts tend to lieanterior to the portal vein branches; however as thebiliary tree spreads out, the position of the duct

relative to the portal branches is highly variable.Don’t assume that a channel anterior to the PVbranch is always a biliary duct—if in doubt, usecolour Doppler to distinguish the bile duct fromthe portal vein or hepatic artery.

The proximal bile duct is best seen either withthe patient supine, using an intercostal approachfrom the right, or turning the patient oblique,right side raised. This projects the duct overthe portal vein, which is used as an anatomicmarker.

Scanning the distal duct usually requires moreeffort. Right oblique or decubitus positions areuseful. Gentle pressure to ease the duodenal gasaway from the duct can also be successful.Sometimes, filling the stomach with water (whichalso helps to display the pancreas) and allowing itto trickle through the duodenum does the trick.Try also identifying the duct in the pancreatic head(Fig. 2.37) and then tracing it retrogradelytowards the liver. Asking the patient to take deepbreaths is occasionally successful, but may makematters worse by filling the stomach with air. It isdefinitely worth persevering with your technique,particularly in jaundiced patients.

SOME COMMON REFERRAL PATTERNSFOR HEPATOBILIARY ULTRASOUND

There is an almost infinite number of reasons forperforming abdominal ultrasound. Some of themore common referrals are discussed below.


Figure 2.36 A persistently, mildly dilated ductpostcholecystectomy (8.5 mm).

Figure 2.37 The common bile duct (arrow) seen on thehead of pancreas on transverse section.

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JaundiceThis symptom is a frequent cause of referral forabdominal ultrasound. It is therefore essential forthe sonographer to have a basic understanding ofthe various mechanisms in order to maximize thediagnostic information from the ultrasound scan.The causes and ultrasound appearances of jaundiceare dealt with more fully in Chapters 3 and 4; abrief overview is included here.

Jaundice, or hyperbilirubinaemia, is an elevatedlevel of bilirubin in the blood. It is recognized bya characteristic yellow coloration of the skin andsclera of the eye, often accompanied by itching ifprolonged.

Bilirubin is derived from the haem portion ofhaemoglobin. Red blood cells are broken down inthe liver into haem and globin, releasing theirbilirubin, which is non-soluble. This is termedunconjugated bilirubin. This is then taken up bythe liver cells and converted to a water-solubleform, conjugated bilirubin, which is excreted viathe biliary ducts into the duodenum to aid fatdigestion.

By knowing which of these two types of bilirubinis present in the jaundiced patient, the cliniciancan narrow down the diagnostic possibilities. Ultrasound then further refines the diagnosis(Fig. 2.38).


Red blood corpuscle

Haemoglobin Haemolysis

Cirrhosis

Prehepatic

BILIRUBIN

Hepatic

Posthepatic

Hepatitis

Tumour

Ductal stones Ductal carcinoma

Pancreatic head inflammation or carcinoma

Ampulla carcinoma

Figure 2.38 Some common causes of jaundice.

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Jaundice can fall into one of two categories:

● obstructive (sometimes called posthepatic) inwhich the bile is prevented from draining outof the liver because of obstruction to thebiliary duct(s)

● non-obstructive (prehepatic or hepatic) inwhich the elevated bilirubin level is due tohaemolysis (the breakdown of the red bloodcells) or a disturbance in the mechanism ofthe liver for uptake and storage of bilirubin,such as in inflammatory or metabolic liverdiseases.

Naturally, the treatment of jaundice depends on itscause (Table 2.1). Ultrasound readily distinguishesobstructive jaundice, which demonstrates somedegree of biliary duct dilatation, from non-obstructive, which does not.

Abnormal liver function testsAltered or deranged liver function tests (LFTs) areanother frequent cause of referral for abdominalultrasound.

Biochemistry from a simple blood test is oftena primary pointer to pathology and is invariablyone of the first tests performed as it is quick andeasily accessible. Most of these markers arehighly unspecific, being associated with manytypes of diffuse and focal liver pathology. Themost frequently encountered LFTs are listed inTable 2.2.

Other common reasons for referralIn some cases, the presenting symptoms may beorgan-specific or even pathognomonic, simplifyingthe task of ultrasound diagnosis. Often, however,


Table 2.1 Common causes of jaundice

Non-obstructive Obstructive

Unconjugated hyperbilirubinaemia Conjugated hyperbilirubinaemia—haemolysis —stones in the biliary duct—haematoma —carcinoma of the duct, head of pancreas or ampulla—Gilbert’s disease —acute pancreatitis

—other masses which compress the common bile duct (e.g. lymph node mass)—biliary atresia

Mixed hyperbilirubinaemia—hepatitis—alcoholic liver disease—cirrhosis of all types—multiple liver metastases—drug-induced liver disease

(See Chapters 3 and 4 for further information.)

Table 2.2 Common serum liver function tests

Test Association with increased level

Bilirubin Obstructive or non-obstructive jaundice. (Differentiation can be made between conjugatedand unconjugated bilirubin)

Alkaline phosphatase Non-obstructive jaundice(ALP) (liver enzyme) Metastases

Other focal hepatic lesionsAlpha fetoprotein Hepatocellular carcinoma (HCC)Prothrombin time Malignancy

Diffuse liver disease (often with portal hypertension)

Gamma glutamyl Obstructive jaundicetransferase Alcoholic liver disease

Alanine amino- Obstructive or transferase (ALT) non-obstructive jaundice

Aspartate amino- Hepatitistransferase (AST) Viral infections(liver enzymes) Other organ failure (e.g. cardiac)

Protein Lack of protein is associated (serum albumin) with numerous liver diseases.

Low levels are associated with ascites, often due to portal hypertension

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the symptoms are vague and non-specific, requir-ing the sonographer to perform a comprehensiveand knowledgeable search. The non-invasivenature of ultrasound makes it ideal for the first-lineinvestigation.

Upper abdominal pain● Upper abdominal pain, the origin of which

could be linked to any of the organs, is one ofthe most frequent causes of referral. Thesonographer can narrow the possibilities downby taking a careful history (see Box 2.1).

● Is the pain focal? This may direct thesonographer to the relevant organ, for examplea thick-walled gallbladder full of stones may betender on gentle transducer pressure, pointingto acute or chronic cholecystitis, depending onthe severity of the pain.

● Bear in mind that gallstones are a commonincidental finding which may be a red herring.Always consider multiple pathologies.

● Is the pain related to any event which may givea clue? Fat intolerance might suggest a biliarycause, pain on micturition a urinary tract cause,for example.

● Is it accompanied by other symptoms such as ahigh temperature? This may be associated withan infective process such as an abscess.

● Could it be bowel-related? Generalizedabdominal pain could be due to inflammatoryor obstructive bowel conditions and knowledgeof the patient’s bowel habits is helpful.

● Has the patient had any previous surgery whichcould be significant?

Palpable right upper quadrant mass

A palpable right upper quadrant mass could be dueto a renal, hepatobiliary, bowel-related or othercause. The sonographer should gently palpate toget an idea of the size and position of the mass andwhether or not it is tender. Specifically targetingthe relevant area may yield useful and unexpectedresults, for example a Reidel’s lobe, colonic carci-noma or impacted faeces, which will help to guidethe nature of further investigations.

APPENDIX: UPPER-ABDOMINAL ANATOMY

Diagrams of sectional upper-abdominal anatomyare reproduced here for quick reference. See Box2.2 for the abbreviations used here.

Box 2.1

Always:● take a verbal history from the patient—don’t

just rely on the request card● obtain the results of any previous investiga-

tions, including previous radiology● consider the possibility of multiple pathologies

Box 2.2 Abbreviations

AO AortaCBD Common bile ductGB GallbladderGDA Gastroduodenal arteryHA Hepatic arteryHOP Head of pancreasIVC Inferior vena cavaLHV Left hepatic veinLL Left lobe of liverLPV Left portal veinLRV Left renal veinMHV Middle hepatic veinR Adr Right adrenal glandRHV Right hepatic veinRK Right kidneyRL Right lobe of liverRPV Right portal veinRRA Right renal arterySA Splenic arterySMA Superior mesenteric arterySMV Superior mesenteric veinSPL SpleenST StomachSV Splenic veinTOP Tail of pancreas

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ST

Caudate lobe

Nect of pancreas

SMV

Uncinate process

RRARLInferior HV

Ligamentum venosum

LHV

LPV

R Adr

Diaphragmatic crus

Figure 2A.2 LS throughthe IVC.

ST

LL

Caudate

Splenic artery

Oesophagus

Coeliac axis

Aorta

Body of pancreas

SV

SMA

LRV

Figure 2A.3 LS through themidline, level of the aorta.

GB

RK

Quadratus lumborum

RL

Figure 2A.1 LS through the rightlobe of the liver.

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ST

Diaphragmatic crus

Spleen

Aorta

LHV

MHV

RHV

Figure 2A.5 Transverse obliquesection through the hepatic venousconfluence.

ST

Gastroduodenal artery

Head of pancreas

CBD

HA

MPV

IVC

Figure 2A.4 Longitudinal obliquesection through the CBD.

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ST

Body of pancreasSVSMA

LRVLRA

Psoas

Ligamentum teres

Duodenum

GB

Gastroduodenalartery

CBD

Quadratus lumborum

Figure 2A.7 TS at thelevel of the pancreas.

HA

ST

SA

Tail of pancreas

Spleen

LK

Ligamentum teres

HA

LPV

RPV

IVC

R Adr

Crus

Figure 2A.6 TS through the level ofthe porta hepatis.

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1. UK Association of Sonographers. 2001 Guidelines forProfessional Working Standards – Ultrasound Practice.UKAS, London.

2. Couinaud C. 1954 Lobes et segments hépatiques; notesur l’architecture anatomique et chirugicale du foie.Presse Medical 62: 709.

3. Conlon RM, Bates JA. 1996 Segmental Localisation ofFocal Hepatic Lesions – A Comparison of Ultrasoundand MRI. Conference proceedings of BMUS,Edinburgh.

4. Cheng Y, Huang T, Chen C et al. 1997 Variations ofthe middle and inferior right hepatic vein: applicationin hepatectomy. Journal of Clinical Ultrasound 25:175–182.

5. Goyal AK, Pokharna DS, Sharma SK. 1990 Ultrasonicmeasurements of portal vasculature in diagnosis ofportal hypertension. Journal of Ultrasound inMedicine 9: 45.

6. Gaiani S, Bolondi L, Li Bassi S et al. 1989 Effect ofmeal on portal hemodynamics in healthy humans andin patients. Hepatology 9: 815–819.

7. Davies RP, Downey PR, Moore WR, Jeans PL, Toouli J. 1991 Contrast cholangiography versusultrasonographic measurement of the ‘extrahepatic’ bile duct: a two-fold discrepancy revisited. Journal ofUltrasound in Medicine 10: 653–657.

References

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Ultrasound is an essential first-line investigation insuspected gallbladder and biliary duct disease. It ishighly sensitive, accurate and comparatively cheapand is the imaging modality of choice.1 Gallbladderpathology is common and is asymptomatic in over13% of the population.2

CHOLELITHIASIS

The most commonly and reliably identified gall-bladder pathology is that of gallstones (see Table3.1). More than 10% of the population of the UKhave gallstones. Many of these are asymptomatic,which is an important point to remember. When

Chapter 3

Pathology of the gallbladder and biliary tree

41

CHAPTER CONTENTS

Cholelithiasis 41Ultrasound appearances 42Choledocholithiasis 45Biliary reflux and gallstone pancreatitis 47Further management of gallstones 47

Enlargement of the gallbladder 48Mucocoele of the gallbladder 48Mirizzi syndrome 48

The contracted or small gallbladder 50Porcelain gallbladder 50Hyperplastic conditions of the gallbladder wall 51

Adenomyomatosis 51Polyps 53Cholesterolosis 53

Inflammatory gallbladder disease 54Acute cholecystitis 54Chronic cholecystitis 56Acalculous cholecystitis 56Complications of cholecystitis 57

Obstructive jaundice and biliary duct dilatation 58Assessment of the level of obstruction 58Assessment of the cause of obstruction 61Management of biliary obstruction 64Intrahepatic tumours causing biliaryobstruction 64Choledochal cysts 64Cholangitis 66

Biliary dilatation without jaundice 66Postsurgical CBD dilatation 66Focal obstruction 67

Pitfalls 67Obstruction without biliary dilatation 67

Early obstruction 67Fibrosis of the duct walls 67

Other biliary diseases 67Primary sclerosing cholangitis 67Caroli’s disease 68Parasites 70

Echogenic bile 71Biliary stasis 71Haemobilia 72Pneumobilia 72

Malignant biliary disease 73Primary gallbladder carcinoma 73Cholangiocarcinoma 74Gallbladder metastases 76

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scanning a patient with abdominal pain it shouldnot automatically be assumed that, when gallstonesare present, they are responsible for the pain. It isnot uncommon to find further pathology in thepresence of gallstones and a comprehensive upper-abdominal survey should always be carried out.

Gallstones are associated with a number of con-ditions. They occur when the normal ratio ofcomponents making up the bile is altered, mostcommonly when there is increased secretion of cho-lesterol in the bile. Conditions which are associatedwith increased cholesterol secretion, and thereforethe formation of cholesterol stones, include obesity,diabetes, pregnancy and oestrogen therapy. Theincidence of stones also rises with age, probablybecause the bile flow slows down.

An increased secretion of bilirubin in the bile, asin patients with cirrhosis for example, is associatedwith pigment (black or brown) stones.

Ultrasound appearancesThere are three classic acoustic properties associ-ated with stones in the gallbladder; they are highlyreflective, mobile and cast a distal acoustic shadow.In the majority of cases, all these properties aredemonstrated (Figs 3.1–3.3).

Shadowing

The ability to display a shadow posterior to a stonedepends upon several factors:

● The reflection and absorption of sound by thestone. This is fairly consistent, regardless of thecomposition of the stone.

● The size of the stone in relation to the beamwidth. A shadow will occur when the stone


Table 3.1 Gallstones—clinical features

Often asymptomaticBiliary colic—RUQ pain, fatty intolerance+ve ultrasound Murphy’s sign (if inflammation is present)Recurring (RUQ) pain in chronic cholecystitisJaundice (depending on degree of obstruction)Fluctuating fever (if infection is present)

RUQ=right upper quadrant.

A

B

Figure 3.1 (A) Longitudinal section and (B) transversesection images of the gallbladder containing stones withstrong distal acoustic shadowing. Note the thickenedgallbladder wall.

Figure 3.2 Multiple tiny stones combining to form aposterior band of shadow.

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fills the width of the beam (Fig. 3.4). Thiswill happen easily with large stones, but asmall stone may occupy less space than thebeam, allowing sound to continue behind it, so a shadow is not seen. Small stones must therefore be within the focal zone

(narrowest point) of the beam and in thecentre of the beam to shadow (Fig. 3.5).Higher-frequency transducers have betterresolution and are therefore more likely to display fine shadows than lowerfrequencies.

PATHOLOGY OF THE GALLBLADDER AND BILIARY TREE 43

Figure 3.3 Floating stones just below the anterior gallbladder wall.

a b c d

Shadow No shadow

Figure 3.4 (a) A shadow will be displayed from the stone, which occupies the width of the beam. (b) The stone issmaller than the beam. (c) The stone is large, but just out of the beam. (d) The stone is large, but outside the focalzone, where the beam is wider.

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● The machine settings must be compatible withdemonstrating narrow bands of shadowing.The fluid-filled gallbladder often displaysposterior enhancement, or increased through-transmission. If the echoes posterior to thegallbladder are ‘saturated’ this will mask fineshadows. Turn the overall gain down to displaythis better (Fig. 3.6). Some image-processingoptions may reduce the contrast between theshadow and the surrounding tissue, so makesure a suitable dynamic range and imageprogramme are used.

● Bowel posterior to the gallbladder may cast itsown shadows from gas and other contents,which makes the gallstone shadow difficult to

demonstrate (Fig. 3.7B). This is a particularproblem with stones in the common bile duct(CBD). Try turning the patient to move thegallbladder away from the bowel. The shadowcast by gas in the duodenum, which containsreverberation, should usually be distinguishablefrom that cast by a gallstone, which is sharpand clean.

Reflectivity

The reflective nature of the stone is enhanced by itsbeing surrounded by echo-free bile. In a con-tracted gallbladder the reflectivity of the stone isoften not appreciated because the hyperechoicgallbladder wall is collapsed over it.

Some stones are only poorly reflective, but shouldstill cause a distal acoustic shadow.

Mobility

Most stones are gravity-dependent and this may bedemonstrated by scanning the patient in an erectposition (Fig. 3.7), when a mobile calculus willdrop from the neck or body of the gallbladder tolie in the fundus. Some stones will float, however,forming a reflective layer just beneath the anteriorgallbladder wall with shadowing that obscures therest of the lumen (Fig. 3.3).

When the gallbladder lumen is contracted,either due to physiological or pathological reasons,


A

B

Figure 3.5 (A) The stones are outside the focal zone,and do not appear to shadow well. (B) The focal zone hasbeen moved to the level of the stones, allowing theshadow to be displayed.

Figure 3.6 The shadow behind the gallstone (leftimage) is obscured if the time gain compensation is settoo high behind the gallbladder (right image).

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any stones present are unable to move and this isalso the case in a gallbladder packed with stones.

Occasionally a stone may become impacted in theneck, and movement of the patient is unable to dis-lodge it. Stones lodged in the gallbladder neck orcystic duct may result in a permanently contracted

gallbladder, a gallbladder full of fine echoes due toinspissated (thickened) bile (Fig. 3.8) or a distendedgallbladder due to a mucocoele (see below).

CholedocholithiasisStones may pass from the gallbladder into thecommon duct, or may develop de novo within thecommon duct. Stones in the CBD may obstructthe drainage of bile from the liver, causing obstruc-tive jaundice.

Due to shadowing from the duodenum, ductalstones are often not demonstrated with ultrasoundwithout considerable effort. Usually they are accom-panied by stones in the gallbladder and a degree ofdilatation of the CBD. In these cases the operatorcan usually persevere and demonstrate the stone atthe lower end of the duct. However, the duct may bedilated but empty, the stone having recently passed.

Stones may be seen to move up and down adilated duct. This can create a ball-valve effect sothat obstruction may be intermittent.

It is not unusual to demonstrate a stone in theCBD without stones in the gallbladder, a phenom-enon which is also well-documented followingcholecystectomy (Fig. 3.9). This may be due to asingle calculus in the gallbladder having movedinto the duct, or stone formation within the duct.

It is also important to remember that stones inthe CBD may be present without duct dilatationand attempts to image the entire common duct


A

B

Figure 3.7 (A) Supine and (B) erect viewsdemonstrating movement of the tiny stone into thefundus of the gallbladder. Note how duodenum posteriorto the gallbladder masks the shadow in the erect state.

Figure 3.8 Stone impacted in theneck of the gallbladder. The left-hand image is a TS through theneck demonstrating the impactedstone. The right-hand imagedemonstrates the dilatedgallbladder containing fine echoesfrom inspissated bile.

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A B

Figure 3.9 (A) A stone in a dilated common bile duct (CBD) with posterior shadowing. The gallbladder was dilatedbut did not contain stones. (B) Stone formation in the intrahepatic ducts.

A B

Figure 3.10 (A) Small stone in the CBD causing intermittent obstruction. At the time of scanning, the CBD wasnormal in calibre at 5 mm. The duct walls are irregular, consistent with cholangitis. (B) Endoscopiccholangiopancreatography (ERCP) of a stone in a normal-calibre (5 mm) duct.

with ultrasound should always be made, even if itis of normal calibre at the porta (Fig. 3.10).

Other ultrasound signs to look for are shown inTable 3.2.

Possible complications of gallstones are outlinedin Figure 3.11A. In rare cases, stones may per-forate the inflamed gallbladder wall to form a fis-tula into the small intestine or colon. A large stone

ch03.qxd 6/30/04 5:40 PM Page 46

passing into the small intestine may impact in theileum, causing intestinal obstruction (Fig. 3.11B).

Biliary reflux and gallstone pancreatitisA stone may become lodged in the distal commonbile duct near the ampulla. If the main pancreaticduct joins the CBD proximal to this, bile and pan-

creatic fluid may reflux up the pancreatic duct,causing inflammation and severe pain.

Reflux up the common bile duct may also resultin ascending cholangitis, particularly if the obstruc-tion is prolonged or repetitive. Cholangitis mayresult in dilated bile ducts with mural irregularityon ultrasound, but endoscopic retrograde cholan-giopancreatography (ERCP) is usually superior indemonstrating intrahepatic ductal changes of thisnature.

Bile reflux is also associated with anomalous cys-tic duct insertion (Fig. 3.12), which is more read-ily recognized on ERCP than ultrasound.

Further management of gallstonesERCP demonstrates stones in the duct withgreater accuracy than ultrasound, particularly atthe lower end of the CBD, which may be obscuredby duodenal gas and also allows for sphinctero-tomy and stone removal.

Laparoscopic cholecystectomy is the preferredmethod of treatment for symptomatic gallbladderdisease in an elective setting and has well-recog-nized benefits over open surgery in experienced


Table 3.2 Gallstones—other ultrasound signs tolook for

Acute or chronic cholecystitis

Complications of cholecystitis, e.g. pericholecysticcollectionStone impacted in the neck of gallbladder—mucocoele,hydropsCBD stonesBiliary obstruction—dilatation of the CBD and/orintrahepatic ductsPancreatitisOther causes of RUQ pain unrelated to stones

CBD = common bile duct.

Cholangitis hepatic abscess

Obstructive jaundice

Obstruction causing pancreatitis

Cholecysto- enteric fistula

Acute or chronic cholecystitis

A

Carcinoma

Figure 3.11 (A) The possible complication of gallstones.(Continued)

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hands. Acute cholecystitis is also increasingly man-aged by early laparoscopic surgery, with a slightlyhigher rate of conversion to open surgery than elec-tive cases.3 Laparoscopic ultrasound may be used asa suitable alternative to operative cholangiographyto examine the common duct for residual stonesduring surgery.4 Both ultrasound and cholescintig-raphy are used in monitoring postoperative biliaryleaks or haematoma (Fig. 3.13).

Other, less common options include dissolutiontherapy and extracorporeal shock wave lithotripsy(ESWL). However, these treatments are oftenonly partially successful, require careful patientselection and also run a significant risk of stonerecurrence.5

ENLARGEMENT OF THE GALLBLADDER

Because of the enormous variation in size andshape of the normal gallbladder, it is not possibleto diagnose pathological enlargement by simplyusing measurements. Three-dimensional tech-niques may prove useful in assessing gallbladdervolume6 but this is a technique which is only likelyto be clinically useful in a minority of patients withimpaired gallbladder emptying.

An enlarged gallbladder is frequently referred toas hydropic. It may be due to obstruction of thecystic duct (see below) or associated with numer-ous disease processes such as diabetes, primarysclerosing cholangitis, leptospirosis or in responseto some types of drug.

A pathologically dilated gallbladder, as opposedto one which is physiologically dilated, usuallyassumes a more rounded, tense appearance.

Mucocoele of the gallbladderIf the cystic duct is obstructed, usually by a stonewhich has failed to pass through to the CBD, thenormal flow of bile from the gallbladder is inter-rupted. Chronic cystic duct obstruction causes thebile to be replaced by mucus secreted by the liningof the gallbladder, resulting in a mucocoele. Thebiliary ducts remain normal in calibre.

If the gallbladder looks dilated, make a carefulsearch for an obstructing lesion at the neck; a stonein the cystic duct is more difficult to identify onultrasound as it is not surrounded by echo-free bile(Fig. 3.8).

Mirizzi syndromeMirizzi syndrome is a rare cause of biliaryobstruction in which the cystic duct is obstructedby a stone, which in combination with a sur-rounding inflammatory process compresses andobstructs the common hepatic duct, causing dis-tal biliary duct dilatation. This is associated with alow insertion of the cystic duct into the commonhepatic duct. Occasionally a fistula forms betweenthe hepatic duct and the gallbladder due to ero-sion of the duct wall by the stone. Ultimately thismay lead to gallstone ileus—small-bowel obstructionresulting from migration of a large stone through


BFigure 3.11 cont’d (B) Gallstone Ileus.

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A B

CBD

LOWER END

Figure 3.12 (A) Anomalous insertion of the cystic duct (arrow) into the lower end of the CBD. (B) Appearances ofcase in (A) are confirmed on ERCP. A stone is also present in the duct.

A B

RUQ

Figure 3.13 (A) Postoperative bile collection in the gallbladder bed. (B) Hyperechoic, irregular mass in the gallbladderbed which represents a resolving haematoma after laparoscopic cholecystectomy.

the cholecystoenteric fistula (Fig 3.11B). If thecondition is not promptly diagnosed, recurringcholangitis leading to secondary biliary cirrhosismay result.

On ultrasound the gallbladder may be eitherenlarged or contracted and contain debris. A stoneimpacted at the neck may be demonstrated together

with dilatation of the intrahepatic ducts with anormal-calibre lower common duct (Fig. 3.14).The diagnosis, however, is difficult, and ERCP isgenerally the most successful modality. Althoughrare, it is an important diagnosis as cholecystectomyin these cases has a higher rate of operative and post-operative complications.7

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THE CONTRACTED OR SMALLGALLBLADDER

Postprandial

The most likely cause is physiological and due toinadequate preparation. The normal gallbladderwall is thickened when contracted, and this mustnot be confused with a pathological process.Always enquire what the patient has recently eatenor drunk (Fig. 3.15).

Pathological causes of a small gallbladder

Most pathologically contracted gallbladders con-tain stones.

When the gallbladder cannot be identified, tryscanning transversely through the gallbladderfossa, just caudal to the porta hepatis. Strong shad-owing alerts the sonographer to the possibility of acontracted gallbladder full of stones. The reflectivesurface of the stones and distal shadowing areapparent and the anterior gallbladder wall can bedemonstrated with correct focusing and goodtechnique (Fig. 3.16).

Do not confuse the appearances of a previouscholecystectomy, when bowel in the gallbladderfossa casts a shadow, with a contracted, stone-filledgallbladder.

A less common cause of a small gallbladder isthe microgallbladder associated with cystic fibrosis

(Fig. 3.17). The gallbladder itself is abnormallysmall, rather than just contracted. Cystic fibrosisalso carries an increased incidence of gallstonesbecause of the altered composition of the bile andbile stasis and the wall might be thickened andfibrosed from cholecystitis.

PORCELAIN GALLBLADDER

When the gallbladder wall becomes calcified theresulting appearance is of a solid reflective struc-ture causing a distal shadow in the gallbladderfossa (Fig. 3.18). This can be distinguished from agallbladder full of stones where the wall can usuallybe seen anterior to the shadowing (Fig 3.16).

A porcelain gallbladder probably results from agallbladder mucocoele—a long-standing obstruc-tion of the cystic duct, usually from a stone. Thebile inside the non-functioning gallbladder is grad-ually replaced by watery fluid, the wall becomesfibrotic and thickened and ultimately calcifies.

There is an association between porcelain gall-bladder and gallbladder carcinoma, so a prophylac-tic cholecystectomy is usually performed topre-empt malignant development.8

The shadowing from the anterior gallbladderwall obscures the gallbladder contents, and canmimic bowel in the gallbladder fossa. A plain X-ray also clearly demonstrates the porcelaingallbladder.


Figure 3.14 Mirizzi syndrome: a large stone in theneck of the gallbladder (arrow) is compressing the bileduct, causing intrahepatic duct dilatation. The lower endof the CBD remains normal in calibre.

Figure 3.15 Postprandial, contracted gallbladder, withconsequently thickened wall.

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HYPERPLASTIC CONDITIONS OF THEGALLBLADDER WALL

AdenomyomatosisThis is a non-inflammatory, hyperplastic conditionwhich causes gallbladder wall thickening. It may bemistaken for chronic cholecystitis on ultrasound.

The epithelium which lines the gallbladder wallundergoes hyperplastic change, extending divertic-

ula into the adjacent muscular layer of the wall.These diverticula, or sinuses (known asRokitansky–Aschoff sinuses), are visible within thewall as fluid-filled spaces (Fig. 3.19), which canbulge eccentrically into the lumen, and may con-tain echogenic material or even (normallypigment) stones.

The wall thickening may be focal or diffuse, andthe sinuses may be little more than hypoechoic


A B

Figure 3.16 (A) The gallbladder lumen is filled with stones, causing dense shadowing in the gallbladder fossa. Thethickened gallbladder wall can be demonstrated separately (arrows) from the reflective surface of the stones.(B) A small layer of bile is visible between the stones and the anterior gallbladder wall.

Figure 3.17 Microgallbladder in cystic fibrosis.

Figure 3.18 TS of a porcelain gallbladderdemonstrating a calcified wall with strong acousticshadowing.

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‘spots’ in the thickened wall, or may become quitelarge cavities in some cases.9

Deposits of crystals in the gallbladder wall fre-quently result in distinctive ‘comet-tail’ artefacts.

Often asymptomatic, this may present with bil-iary colic although it is unclear whether this iscaused by co-existent stones. Its distinctive appear-

ance allows the diagnosis to be made easily,whether or not stones are present.

Cholecystectomy is performed in symptomaticpatients, usually those who also have stones.Although essentially a benign condition, a fewcases of associated malignant transformationhave been reported, usually in patients with asso-


A B

C

Figure 3.19 Adenomyomatosis: (A) LS demonstrating a thickened gallbladder wall with a small Rokitansky-Aschoffsinus (arrow) at the fundus. (B) TS demonstrating a stone and comet-tail artifacts from within the wall due to crystaldeposits. (C) TS through a more advanced case of adenomyomatosis with a large Rokitansky–Aschoff sinus, giving theappearance of a ‘double lumen’.

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ciated anomalous insertion of the pancreaticduct.10

PolypsGallbladder polyps are usually asymptomaticlesions which are incidental findings in up to 5%of the population. Occasionally they are the causeof biliary colic. The most common type are cho-lesterol polyps. These are reflective structureswhich project into the gallbladder lumen but donot cast an acoustic shadow. Unless on a longstalk they will remain fixed on turning the patientand are therefore distinguishable from stones(Fig. 3.20).

There is an association between larger adenoma-tous gallbladder polyps and subsequent carcinoma,especially in patients over 50 years of age, so chole-cystectomy is often advised (Fig. 3.20C). Smallerpolyps of less than 1 cm in diameter may be safelymonitored with ultrasound.11 In particular, gall-bladder polyps in patients with primary sclerosingcholangitis have a much greater likelihood ofmalignancy (40–60%).12

CholesterolosisAlso known as the ‘strawberry gallbladder’, thisgets its name because of the multiple tiny noduleson the surface of the gallbladder mucosal lining.


A B

GB

C

Figure 3.20 (A) Small polyp in the gallbladder lumen—no posterior shadowing is evident. (B) A gallbladder polyp on astalk moves with different patient positions. (C) Large, fleshy gallbladder polyp.

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These nodules are the result of a build-up of lipidsin the gallbladder wall and are not usually visibleon ultrasound. However in some cases, multiplepolyps also form on the inner surface, projectinginto the lumen, and are clearly visible on ultra-sound (Fig. 3.21). Cholesterolosis may be asymp-tomatic, or may be accompanied by stones andconsequently requires surgery to alleviate symp-toms of biliary colic.

INFLAMMATORY GALLBLADDER DISEASE

Cholecystitis is usually associated with gallstones;the frictional action of stones on the gallbladderwall causes some degree of inflammation in almostall cases. The inner mucosa of the wall is injured,allowing the access of enteric bacteria. The inflam-matory process may be long-standing and chronic,acute or a combination of acute inflammation on achronic background.

Acute cholecystitisAcute inflammation of the gallbladder presentswith severe RUQ pain localized to the gallbladderarea. The pain can be elicited by (gently!) pressingthe gallbladder with the ultrasound transducer—apositive ultrasound Murphy’s sign. (This sign,although a useful pointer to acute inflammation, is

not specific and can frequently be elicited in otherconditions, such as chronic inflammatory cases.)

On ultrasound, the gallbladder wall is thickenedgreater than 2 mm. This is not in itself a specificsign (see Table 3.3), but characteristically thethickening in acute cholecystitis is symmetrical,affecting the entire wall, and there is an echo-poor‘halo’ around the gallbladder as a result of oede-matous changes (Fig. 3.22). This is not invariable,however, and focal thickening may be present, orthe wall may be uniformly hyperechoic in somecases. Pericholecystic fluid may also be present, andthe inflammatory process may spread to the adja-cent liver.

Colour or power Doppler can be helpful indiagnosing acute cholecystitis and in differentiat-ing it from other causes of gallbladder wall thick-ening. Hyperaemia in acute cholecystitis can bedemonstrated on colour Doppler around thethickened wall13 (Fig. 3.23). In a normal gallblad-der, colour Doppler flow may be seen around thegallbladder neck in the region of the cystic arterybut not elsewhere in the wall. The increased sensi-tivity of power Doppler, as opposed to colour


Figure 3.21 Cholesterolosis TS of the gallbladderdemonstrating multiple tiny polyps in the gallbladder.

Table 3.3 Causes of a thickened gallbladder wall

Physiological—Postprandial

Inflammatory—Acute or chronic cholecystitis—Sclerosing cholangitis—Crohn’s disease—AIDS

Adjacent inflammatory causes—Pancreatitis—Hepatitis—Pericholecystic abscesses

Non-inflammatory—Adenomyomatosis—Gallbladder carcinoma—Focal areas of thickening due to metastases or polyps—Leukaemia

Oedema—Ascites from a variety of causes, including organ

failure, lymphatic obstruction and portal hypertensionVarices

—Varices of the gallbladder wall in portal hypertension

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Doppler, does enable the operator to demonstratevascularity in the normal gallbladder wall and theoperator should be familiar with normal appear-ances for the machine in use when making thediagnosis of acute cholecystitis14 (Fig. 3.24).

Doppler can potentially distinguish acute inflam-mation from chronic disease.15 However, false-positive results can be found in cases of pancreatitisand gallbladder carcinoma and the technique doesnot add significantly to the grey-scale image.

Complications may occur if the acute inflamma-tion progresses (see below) due to infection,pericholecystic abscesses and peritonitis.

Further management of acute cholecystitis

In an uncomplicated acute cholecystitis, analgesiato settle the patient in the short term is followedby the removal of the gallbladder. Open surgery,which is increasingly reserved for the more


A B

C D

Figure 3.22 Acute cholecystitis: (A) TS of an oedematous, thickened gallbladder wall with a stone. (B) LS with athickened wall (arrows). Stones and debris are present. (C) and (D) TS and LS demonstrating pericholecystic fluid.

(Continued)

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complex cases, is giving way to the more frequentuse of laparoscopic cholecystectomy.

If unsuitable for immediate surgery, for examplein cases complicated by peritonitis, the patient ismanaged with antibiotics and/or percutaneousdrainage of pericholecystic fluid or infected bilefrom the gallbladder, usually under ultrasoundguidance. This allows the patient’s symptoms tosettle and reduces morbidity from the subsequentelective operation.16

Hepatobiliary scintigraphy has high sensitivityand specificity for evaluating patients with acutecholecystitis,17 particularly if the ultrasound exam-ination is technically difficult or equivocal and hasthe advantage of being able to demonstrate hepa-tobiliary drainage into the duodenum.

Plain X-ray is seldom used, but can confirm thepresence of gas in the gallbladder.

Chronic cholecystitisUsually associated with gallstones, chronic chole-cystitis presents with lower-grade, recurring rightupper quadrant pain. The action of stones on thewall causes it to become fibrosed and irregularlythickened, frequently appearing hyperechoic (Fig.3.25). The gallbladder is often shrunken and con-tracted, having little or no recognizable lumenaround the stones. Chronic cholecystitis may becomplicated by episodes of acute inflammation ona background of the chronic condition.

Most gallbladders which contain stones show atleast some histological degree of chronic cholecys-titis, even if wall thickening is not apparent onultrasound.

Acalculous cholecystitisInflammation of the gallbladder without stones isrelatively uncommon. A thickened, tender gall-bladder wall in the absence of any other obviouscause of thickening may be due to acalculouscholecystitis. This condition tends to be associatedwith patients who are already hospitalized and havebeen fasting, including post-trauma patients, thoserecovering from surgical procedures and diabeticpatients. It is brought about by bile stasis leadingto a distended gallbladder and subsequentlydecreased blood flow to the gallbladder. This,especially in the weakened postoperative state, canlead to infection. Because no stones are present,the diagnosis is more difficult and may be delayed.Patients with acalculous cholecystitis are thereforemore likely to have severe pain and fever by thetime the diagnosis is made, increasing the inci-dence of complications such as perforation.

The wall may appear normal on ultrasound inthe early stages, but progressively thickens (Fig.3.26). Biliary sludge is usually present and a


E

Figure 3.22 cont’d (E) Normal gallbladder in thepresence of ascites. Oedema may cause the wall tothicken, mimicking an inflammatory process.

Figure 3.23 Colour Doppler demonstrates hyperaemiain the thickened gallbladder wall in acute cholecystitis.

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pericholecystic abscess may develop in the laterstages. A positive Murphy’s sign may help to focuson the diagnosis, but in unconscious patients thediagnosis is a particularly difficult one.

Because patients may already be critically ill withtheir presenting disease, or following surgery, thereis a role for ultrasound in guiding percutaneouscholecystostomy at the bed-side to relieve thesymptoms.18

Chronic acalculous cholecystitis implies a recur-rent presentation with typical symptoms of biliarycolic, but no evidence of stones on ultrasound.Patients may also demonstrate a low ejection frac-tion during a cholecystokinin-stimulated hepaticiminodiacetic acid (HIDA) scan. The symptomsare relieved by elective laparoscopic cholecystec-tomy in most patients, with similar results to thosefor gallstone disease19 (although some are found tohave biliary pathology at surgery, which mightexplain the symptoms, such as polyps, choles-terolosis or biliary crystals/tiny stones in additionto chronic inflamation).

Complications of cholecystitisAcute-on-chronic cholecystitis

Patients with a long-standing history of chroniccholecystitis may suffer (sometimes repeated) attacks

of acute inflammation. The gallbladder wall is thick-ened, as for chronic inflammation, and may becomefocally thickened with both hypo- and hyperechoicregions. Stones are usually present (Fig. 3.27).

Gangrenous cholecystitis

In a small percentage of patients, acute gallbladderinflammation progresses to gangrenous cholecysti-tis. Areas of necrosis develop within the gallbladderwall, the wall itself may bleed and small abscessesform (Fig. 3.28). This severe complication of theinflammatory process requires immediate cholecys-tectomy.

The gallbladder wall is friable and may rupture,causing a pericholecystic collection and possiblyperitonitis. Inflammatory spread may be seen inthe adjacent liver tissue as a hypoechoic, ill-definedarea. Loops of adjacent bowel may become adher-ent to the necrotic wall, forming a cholecystoen-teric fistula.

The wall is asymmetrically thickened and areasof abscess formation may be demonstrated. Thedamaged inner mucosa sloughs off, forming theappearance of membranes in the gallbladder lumen.The gallbladder frequently contains infected debris

The presence of a bile leak may also be demon-strated with hepatobiliary scintigraphy, using tech-netium99, which is useful in identifying a bile


A B

Figure 3.24 Normal gallbladder wall vascularity. (A) In a normal gallbladder, colour Doppler can demonstrate thecystic artery (arrowhead) but does not demonstrate flow near the fundus. (B) Power Doppler is more sensitive and candemonstrate flow throughout the wall (arrows) in a normal gallbladder; this must not be mistaken for hyperaemia.

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collection which may otherwise be obscured bybowel on ultrasound.

Emphysematous cholecystitis

This is a form of acute gangrenous cholecystitis inwhich the inflamed gallbladder may becomeinfected, particularly in diabetic patients, with gas-forming organisms. Both the lumen and the wall ofthe gallbladder may contain air, which is highlyreflective, but which casts a ‘noisy’, less definiteshadow than that from stones. Discrete gas bub-

bles have been reported on ultrasound within thegallbladder wall20 and may also extend into theintrahepatic biliary ducts.21

The air rises to the anterior part of the gallbladder,obscuring the features behind it (Fig. 3.29). Thiseffect may mimic air-filled bowel on ultrasound.

Emphysematous cholecystitis has traditionallyhad a much higher mortality rate than other formsof cholecystitis, requiring immediate cholecystec-tomy. However, improvements in ultrasound reso-lution, and in the early clinical recognition of thiscondition, suggest that it is now being diagnosedearlier and may be managed more conservatively.The gas in the gallbladder may be confirmed on aplain X-ray (Fig. 3.30), but ultrasound is more sen-sitive in demonstrating the earlier stages.

Gallbladder empyema

Empyema is a complication of cholecystitis in whichthe gallbladder becomes infected behind anobstructed cystic duct. Fine echoes caused by pusare present in the bile (Fig. 3.31). These patients areoften very ill with a fever and acute pain. A peri-cholecystic gallbladder collection may result fromleakage through the gallbladder wall with subse-quent peritonitis. Ultrasound may be used to guidea bedside drainage in order to allow the patient’ssymptoms to settle before surgery is attempted.22

OBSTRUCTIVE JAUNDICE AND BILIARYDUCT DILATATION

Dilatation of all or part of the biliary tree is usuallythe result of proximal obstruction. Less commonlythe biliary tree may be dilated but not obstructed(Table 3.4). The most common causes of obstruc-tion are stones in the common duct or a neoplasmof the bile duct or head of pancreas.

The patient with obstructive jaundice may pres-ent with upper abdominal pain, abnormal liverfunction tests (LFTs) (see Chapter 2) and, if theobstruction is not intermittent, the sclera of theeye and the skin adopt a yellow tinge.

Assessment of the level of obstructionIt is possible for the sonographer to work outwhere the obstructing lesion is situated by observ-


A

B

Figure 3.25 Chronic cholecystitis. (A) A hyperechoic,irregular, thickened wall. The gallbladder contains a smallstone and thickened, echogenic bile. It was mildly tenderon scanning. (B) The wall is focally thickened anteriorly,and the gallbladder contains a large stone and a polyp inthe fundus.

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ing which parts of the biliary tree are dilated (Fig.3.32):

● Dilatation of the common bile duct (that is,that portion of the duct below the cystic ductinsertion) implies obstruction at its lower end.

● Dilatation of both biliary and pancreatic ductsimplies obstruction distally, at the head of thepancreas or ampulla of Vater. This is morelikely to be due to carcinoma of the head ofpancreas, ampulla or acute pancreatitis than astone. However, it is possible for a stone to be


A B

Figure 3.26 (A) Acalculous cholecystitis. The gallbladder wall is markedly thickened and tender on scanning.(B) Gravity-dependent sludge with a thick, oedematous wall. No stones were present.

Figure 3.27 Acute on chronic cholecystitis. A patientwith known gallstones and chronic cholecystitis presentswith an episode of acute gallbladder pain. The wall isconsiderably more thickened and hyperechoic than onprevious scans.

Figure 3.28 Gangrenous cholecystitis. The gallbladderwall is focally thickened and an intramural abscess hasformed on the anterior aspect.

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lodged just distal to the confluence of thebiliary and pancreatic ducts.

● Dilatation of the gallbladder alone (that iswithout ductal dilatation) is usually caused by,obstruction at the neck or cystic duct (Fig. 3.8).

To assess whether the gallbladder is pathologi-cally dilated may be difficult on ultrasound. Thesonographer should look at both the size and

shape; the dilated gallbladder will have a rounded,bulging shape due to the increase in pressure insideit. A gallbladder whose wall has become fibrosedfrom chronic cholecystitis due to stones will oftenlose the ability to distend, so the biliary ducts canlook grossly dilated despite the gallbladder remain-ing ‘normal’ in size, or contracted.

Early ductal obstruction

Beware very early common duct obstruction, beforethe duct becomes obviously dilated. The duct maybe mildly dilated at the lower end, just proximal to astone. Likewise intermittent obstruction by a smallstone at the lower end of the duct may be non-dilated by the time the scan is performed (Fig. 3.10).

A significant ultrasound feature in the absenceof any other identifiable findings is that of thicken-ing of the wall of the bile duct. This represents aninflammatory process in the duct wall, which maybe found in patients with small stones in a non-dilated duct, but is also associated with sclerosingcholangitis.23

It is sometimes technically difficult in somepatients (particularly those with diffuse liver dis-ease) to work out whether a tubular structure on


A

B

C

Figure 3.29 Emphysematous cholecystitis. (A) and (B)TS and LS with gas and debris in the gallbladder lumen.(C) Gas in the gallbladder lumen completely obscures thecontents.

Figure 3.30 X-ray demonstrating gas in the gallbladderin emphysematous cholecystitis.

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ultrasound represents a dilated duct or a blood ves-sel. Colour Doppler will differentiate the dilatedbile duct from a branch of hepatic artery or portalvein (Fig. 3.33).

Assessment of the cause of obstructionThe numerous causes of biliary dilatation are sum-marized in Table 3.4. Frequently, ultrasound diag-

noses obstruction but does not identify the cause.This is a good case for perseverance by the opera-tor, as the lower end of the CBD is visible inthe majority of cases once overlying duodenumhas been moved away (Figs 3.9, 3.10 and 33.4).However, ultrasound is not generally regarded as areliable tool for identifying ductal stones and isfrequently unable to diagnose ductal strictures,especially those from benign causes.


C D

A B

Figure 3.31 Gallbladder empyema. (A) and (B) LS and TS of the same gallbladder. The gallbladder has ruptured,forming a cholecystoenteric fistula which had resealed at surgery. The gallbladder contains pus and stones, with severalanterior septations, forming pockets of infected bile which also contained stones (arrows). (C) CT scan confirming theultrasound appearances. (D) Gallbladder empyema demonstrating a large gallbladder full of pus and stones.

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Figure 3.32 Sites of possible gallstone obstruction.

A B

PV

HA

LOBESAG RT

Figure 3.33 (A) Dilated biliary ducts do not demonstrate flow on colour Doppler, differentiating them from portalvessels. (B) Originally suspected as a dilated biliary tree, colour Doppler demonstrates that the ‘extra tubes’ are, in fact,dilated intrahepatic arteries in a patient with end-stage chronic liver disease with reversed portal venous flow.

ERCP, although invasive, is a more accuratemethod of examining the CBD and will often iden-tify strictures or small calculi not visible on ultra-sound. It has the advantage of a therapeutic role in

addition to its diagnostic capabilities, by allowingthe extraction of stones at the time of diagnosis. Itis associated with a small risk of complication, how-ever, and its use is therefore increasingly limited infavour of the non-invasive magnetic resonancecholangiopancreatography (MRCP) (Fig. 3.34F).MRCP has been found to be highly effective inthe diagnosis of CBD stones24 and can potentiallyavoid the use of purely diagnostic ERCP.25

Table 3.4 Causes of biliary duct dilatation

Intrinsic—Stones—Carcinoma of the ampulla of Vater—Cholangiocarcinoma—Stricture (associated with chronic pancreatitis)—Biliary atresia/choledochal cyst—Post-liver-transplantation bile duct stenosis (usually

anastomotic)—Parasites—Age-related or post-surgical mild CBD dilatation

Extrinsic—Carcinoma of the head of pancreas—Acute pancreatitis—Lymphadenopathy at the porta hepatis—Other masses at the porta, e.g. hepatic artery

aneurysm, gastrointestinal tract mass—Intra-hepatic tumours (obstruct distal segments)

Diffuse hepatic conditions—Sclerosing cholangitis—Caroli’s disease

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A B

D

CYSTIC DUCT

STONE

C

FE

Figure 3.34 (A) Duodenal gas obscures the cause of obstruction at the lower end of this dilated CBD. (B) Patientpositioning can move bowel gas away from the duct, demonstrating the cause of obstruction—a stone at the lowerend. (C) TS of a dilated CBD in the head of the pancreas (arrow). (D) Dilated CBD with a hypoechoic ampullarycarcinoma at the lower end (arrows). (E) Intrahepatic bile duct dilatation. (F) MRCP, post-cholecystectomy, showingstones in the CBD and cystic duct stump.

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CT and MRI are useful for staging purposes if theobstructing lesion is malignant. Cholangiocarci-nomas spread to the lymph nodes and to the liverand small liver deposits are particularly difficult torecognize on ultrasound if the intrahepatic biliaryducts are dilated.

In hepatobiliary scintigraphy, technetium99m-labelled derivatives of iminodiacetic acid areexcreted in the bile and may help to demonstratesites of obstruction, for example in the cystic duct,or abnormal accumulations of bile, for examplecholedochal cysts.

Courvoisier’s law, to which there are numerousexceptions, states that if the gallbladder is dilatedin a jaundiced patient, then the cause is not due toa stone in the common duct. The reason for this isthat, if stones are or had been present, then thegallbladder would have a degree of wall fibrosisfrom chronic cholecystitis which would prevent itfrom distending. In fact there are many exceptionsto this ‘law’ which include the formation of stonesin the duct, without gallbladder stones, and alsoobstruction by a pancreatic stone at the ampulla.Thus:

● Do not assume that obstructive jaundice in apatient with gallstones is due to a stone in theCBD. The jaundice may be attributable toother causes.

● Do not assume that obstructive jaundicecannot be due to a stone in the CBD if thegallbladder does not contain stones. A solitarystone can be passed into the duct from thegallbladder or stones can form within the duct.

Management of biliary obstructionManagement of biliary obstruction obviouslydepends on the cause and the severity of the con-dition. Removal of stones in the CBD may be per-formed by ERCP with sphincterotomy. Electivecholecystectomy may take place if gallstones arepresent in the gallbladder.

Laparoscopic ultrasound is a useful adjunct tosurgical exploration of the biliary tree and its accu-racy in experienced hands equals that of X-raycholangiography. It is rapidly becoming the imag-ing modality of choice to examine the ducts duringlaparoscopic cholecystectomy.26

Endoscopic ultrasound can also be used toexamine the CBD, avoiding the need for laparo-scopic exploration of the duct when performed inthe immediate preoperative stage.27

The treatment of malignant obstruction isdetermined by the stage of the disease. Accuratestaging is best performed using CT and/or MRI.If surgical removal of the obstructing lesion is nota suitable option because of local or distant spread,palliative stenting may be performed endoscopi-cally to relieve the obstruction and decompress theducts (Fig. 3.35). The patency of the stent may bemonitored with ultrasound scanning by assessingthe degree of dilatation of the ducts.

Clinical suspicion of early obstruction should beraised if the serum alkaline phosphatase is elevated,(often more sensitive in the early stages than araised serum bilirubin). In the presence of ductaldilatation on ultrasound, further imaging, such asCT or MRCP, may then refine the diagnosis.

Intrahepatic tumours causing biliaryobstructionFocal masses which cause segmental intrahepaticduct dilatation are usually intrinsic to the ductitself, for example cholangiocarcinoma.

It is also possible for a focal intrahepatic mass,whether benign or malignant, to compress anadjacent biliary duct, causing subsequent obstruc-tion of that segment. This is not, however, a com-mon cause of biliary dilatation and occurs mostusually with hepatocellular carcinomas.28 Mostliver metastases deform rather than compress adja-cent structures and biliary obstruction only occursif the metastases are very large and/or invade thebiliary tree. A hepatocellular carcinoma or metasta-tic deposit at the porta hepatis may obstruct thecommon duct by squeezing it against adjacentextrahepatic structures. Benign intrahepatic lesionsrarely cause ductal dilatation, but occasionally theirsheer size obstructs the biliary tree.

Choledochal cystsMost commonly found in children, this is associ-ated with biliary atresia, in which the distal ‘blind’end of the duct dilates into a rounded, cystic massin response to raised intrahepatic pressure.

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Choledochal cysts in adults are rare, and tend tobe asymptomatic unless associated with stones orother biliary disease. They are sometimes associatedwith an anomalous insertion of the CBD into thepancreatic duct. The mechanism of the subsequentcholedochal cyst formation is unclear, but it isthought that the common channel, which drainsinto the duodenum, is prone to reflux of pancreaticenzymes into the biliary duct. This can cause a bil-

iary stricture, with subsequent proximal dilatation ofthe duct, forming a choledochal cyst29 [Fig. 3.36].

Less commonly the dilatation is due to a non-obstructive cause in which the biliary ducts them-selves become ectatic and can form diverticula.This may be due to a focal stricture of the ductwhich causes reflux and a localized enlargement ofthe duct proximal to the stricture. (See alsoCaroli’s disease, below (Fig. 3.42.)


A B

Figure 3.35 (A) This dilated CBD is obstructed by a mass (arrows) invading the lower end. (B) ERCP demonstrates a tight, malignant stricture, and can be used to position a palliative stent. (C) Stent in the CBD of a patient with acholangiocarcinoma and malignant ascites. Decompression of the dilated biliary tree has been achieved, and ultrasoundcan be used to monitor the patency of the stent.

C

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Complications of choledochal cysts includecholangitis, formation of stones and progression ofthe condition to secondary biliary cirrhosis, whichmay be associated with portal hypertension.

It may be difficult to differentiate a choledochalcyst, particularly if solitary, from other causes ofhepatic cysts. The connection between the chole-dochal cyst and the adjacent biliary duct may bedemonstrated with careful scanning.

CholangitisCholangitis is an inflammation of the biliary ducts,most commonly secondary to obstruction.

It is rarely possible to distinguish cholangitisfrom simple duct dilatation on ultrasound,although in severe cases the ductal walls appearirregular (Fig. 3.10A) and debris can be seen in thelarger ducts (Fig. 3.37).

The walls of the ducts may appear thickened.Care should be taken to differentiate this appear-ance from tumour invasion and further imaging isoften necessary to exclude malignancy.

Bacterial cholangitis is the most common form,due to bacterial infection which ascends the biliarytree. Bacterial cholangitis is also associated withbiliary enteric anastomoses. It may be complicatedby abscesses if the infection is progressive and

untreated. Small abscesses may be difficult to diag-nose on ultrasound, as they are frequently iso-echoic and ill-defined in the early stages and biliarydilatation makes evaluation of the hepaticparenchyma notoriously difficult.

Contrast CT will often identify small abscessesnot visible on ultrasound, and MRCP or ERCPdemonstrates mural changes in the ducts.

Other forms of cholangitis include:

● Primary sclerosing cholangitis, a chronic,progressive cholestatic disease, which exhibitsductal thickening, focal dilatation and strictures(see p. 67).

● AIDS-related cholangitis which causes changessimilar to that of primary sclerosing cholangitis.

● Recurrent pyogenic cholangitis (Orientalcholangiohepatitis) which is endemic inSoutheast Asia and is associated with parasitesand malnutrition. Intrahepatic biliary stones arealso a feature of this condition.

BILIARY DILATATION WITHOUT JAUNDICE

Postsurgical CBD dilatationIn patients who have had cholecystectomy associatedwith previous dilatation of the CBD it is common tofind a persistent (but non-significant) mild dilatationof the duct postoperatively. The serum alkaline


Figure 3.36 Choledochal cyst. (These can sometimes bedifficult to distinguish from a gallbladder, particularly iflarge.)

Figure 3.37 Cholangitis with debris present in thedilated CBD (arrows).

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phosphatase and bilirubin levels should be normal inthe absence of pathology. Because stones may befound in the duct postoperatively, it is important todifferentiate non-obstructive from truly obstructivedilatation in a symptomatic patient (Fig. 3.38). If indoubt, the patient may be rescanned at a suitableinterval to assess any increase in ductal diameter.

Focal obstructionIntrahepatic tumour, such as cholangiocarcinoma,may obstruct a segment of the biliary tree whilstthe remainder of the liver and biliary tree appearsnormal. Focal duct dilatation should trigger theoperator to examine the proximal area of dilatationfor a possible mass. Such tumours may be presentbefore jaundice is clinically apparent.

PitfallsPatients with cirrhosis and portal hypertension mayhave dilated hepatic arteries which can mimic theappearances of dilated ducts. Colour or powerDoppler will readily differentiate between these, asthe bile duct lacks a Doppler signal. Pneumobilia(air in the ducts) casts a distal acoustic shadow, andmay therefore obscure ductal dilatation.

OBSTRUCTION WITHOUT BILIARYDILATATION

Early obstructionIt is possible to scan a patient at the time of recentonset of obstruction from a stone before the ductshave had time to dilate, leading to a false-negativediagnosis. If clinical suspicion persists, a rescan isfrequently useful in these cases.

Occasionally, stones have a ball-valve effect inthe duct, causing intermittent obstruction whichmay not demonstrate ductal dilatation on theultrasound scan.

Fibrosis of the duct wallsThere are a number of chronic pathological condi-tions which cause the walls of the ducts to becomefibrotic and stiff. These include primary sclerosingcholangitis (see below), hepatitis and other chronichepatic diseases leading to cirrhosis. The liver itselfbecomes rigid and this prevents biliary dilatation.In such cases the lack of dilated bile ducts does notnecessarily imply an absence of obstruction.

OTHER BILIARY DISEASES

Primary sclerosing cholangitis (PSC)PSC is a chronic hepatobiliary disease in which thewalls of the bile ducts become inflamed, causingnarrowing. It occurs predominantly in young men(with a 2:1 male to female ratio) and is character-ized by multiple biliary strictures and bead-likedilatations of the ducts. The aetiology of PSCremains unclear but is associated with inflamma-tory bowel disorders or may be idiopathic.

Clinical features include jaundice, itching andfatigue. Some 25% of patients also have gallstones,which complicates the diagnosis. Approximately70% of patients affected also have ulcerative colitis.

It is progressive gradual fibrosis which eventu-ally obliterates the biliary tree. Untreated, thiseventually leads to hepatic failure. PSC has a strongassociation with cholangiocarcinoma, and it is this,rather than hepatic failure, which may lead todeath. In the absence of malignancy, however,hepatic transplant has a 70–90% 5-year survivalrate.30


Figure 3.38 Biliary dilatation following laparoscopiccholecystectomy, due to a surgical clip across the CBD.

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Ultrasound appearances

The ultrasound appearances in PSC may be normalor may demonstrate a coarse, hyperechoic texturethroughout the liver. Ductal strictures may causedownstream dilatation in some segments (Fig. 3.39)and in some cases there is marked biliary dilatation,but in the majority of patients the biliary ducts areprevented from dilatation by the surrounding fibro-sis and so appear unremarkable on ultrasound.MRCP is superior at demonstrating intrahepaticductal strictures. Mural thickening, particularly inthe CBD, may be demonstrated with careful, high-resolution scanning31 (Fig. 3.40).

Ultrasound also demonstrates the effects of por-tal hypertension in advanced disease. The gallblad-der may also have a thickened wall and can bedilated.32

Due to the association between PSC andcholangiocarcinoma, which may be multifocal, acareful search must be made for mass lesions.Because the ultrasound appearances may be thoseof a coarse, nodular liver texture, it is difficult toidentify small cholangiocarcinomas and colour orpower Doppler may be an advantage here (Fig.3.41). This diagnosis is an important one, becausethe patient’s prognosis and management areaffected by the presence of cholangiocarcinomata.If no masses are identified, the prognosis is goodand includes the endoscopic removal of stones torelieve symptoms, endoscopic stenting of mainduct strictures to relieve jaundice and subsequentliver transplant to pre-empt the formation of carci-noma. However, if carcinoma is already present, 5-year survival falls to 10%.

Caroli’s disease (congenital intrahepaticbiliary dilatation)This is a rare, congenital condition in which thebile ducts are irregularly dilated with diverticula-like projections. These diverticula may becomeinfected and may separate off from the biliary duct,forming choledochal cysts (Fig. 3.42).

In most cases, the entire hepatobiliary system isaffected to some degree. Sufferers may present inearly childhood, with symptoms of portal hyper-tension, 33 or may remain well until adulthood, pre-senting with cholangitis. It is generally thought to

be an autosomal recessive inherited condition andthe prognosis is poor. Medical control of associatedportal hypertension with varices can improve thequality of life.

In a few cases, the disease is confined to one ortwo segments of the liver, in which case a cure canbe effected with hepatic resection.34 The extrahep-atic biliary tree is often unaffected.


A

B

Figure 3.39 (A) Localized biliary dilatation due to aductal stricture in a patient with primary sclerosingcholangitis (PSC). (B) Coarse-textured liver with a dilatedCBD in PSC. A small choledochal cyst is present justanterior to the lower CBD.

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A BFigure 3.40 PSC. Hyperechoic mural thickening of the biliary tree can be seen in (A) the CBD and (B) the intrahepaticducts.

A B

NORMAL 1836 HZ

5.1mm

Figure 3.41 PSC. (A) A tiny, suspicious, hyperechoic focal lesion (arrow) demonstrates increased flow on colourDoppler. (B) The spectral waveform confirms vigorous arterial flow in this small cholangiocarcinoma.

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The ultrasound appearances are usually of wide-spread intrahepatic duct dilatation, with both sac-cular and fusiform biliary ectasia. Because it is alsoassociated with biliary stone formation, the diag-nosis is often not clear. The dilatation is also asso-ciated with cholangitis and signs of infection maybe present in the form of debris within the ducts.Sometimes, frank choledocal cysts can be located.

Advanced disease is associated with portal hyper-tension and, in some cases, cholangiocarcinoma.35

ParasitesParasitic organisms, such as the Ascaris worm andliver fluke, are extremely rare in the UK. However,they are a common cause of biliary colic in Africa,


A

kr

C

B D

Figure 3.42 Caroli’s disease. (A) Dilated biliary tree and ascites. (B) TS of a different patient with end-stage disease.The grossly abnormal liver texture contrasts with the right kidney. (C) A small section of focal CBD dilatation persistedin a symptomatic patient, with normal-calibre distal CBD. This was confirmed on ERCP and thought to be a dyskineticsegment, causing biliary reflux, but was later diagnosed as a mild form of Caroli’s. (D) 3D CT reconstruction of the casein (C), confirming the ultrasound appearances. Note the tiny ectatic ‘pouchings’ of the intrahepatic ducts characteristicof Caroli’s.

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the Far East and South America. The hyperechoiclinear structures in the gallbladder lumen shouldraise the sonographer’s suspicion in patients nativeto, or who have visited these countries. Impactedworms in the biliary ducts may mimic other ductalmasses.36

They are a rare cause of obstructive biliarydilatation (Fig. 3.43).

Patients may present with acute cholangitis orabdominal pain and vomiting. Endoscopic man-agement is frequently highly effective.37

ECHOGENIC BILE

Biliary stasisFine echoes in the bile within the gallbladder arenot uncommon on an ultrasound scan. This iscommonly due to the inspissation of bile followingprolonged starving, for example following surgery(Fig. 3.44). These appearances disappear after anormal diet is resumed and the gallbladder hasemptied and refilled.

It occurs when the solutes in the bile precipitate,often due to hypomotility of the gallbladder, andcan commonly be seen following bone marrowtransplantation and in patients who have under-gone prolonged periods (4–6 weeks) of total par-enteral nutrition.38

Prolonged biliary stasis may lead to inflamma-tion and/or infection, particularly in post-operative patients and those on immunosuppression(Fig. 3.44B). Its clinical course varies from com-

plete resolution to progression to gallstones.However, following the resumption of oral feed-ing, the gallbladder may contract and empty thesludge into the biliary tree causing biliary colic,acute pancreatitis and/or acute cholecystitis.39 Forthis reason, cholecystectomy may be considered insymptomatic patients with biliary sludge.

The fine echoes may form a gravity-dependentlayer and may clump together, forming ‘sludgeballs’. To avoid misdiagnosing sludge balls aspolyps, turn the patient to disperse the echoes or


Figure 3.43 Ascaris worm in the gallbladder.

A

B

Figure 3.44 (A) Inspissated bile in the normalgallbladder of a fasting patient. (B) Gravity-dependentbiliary sludge with a small stone.

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rescan after the patient has resumed a normaldiet.

Biliary stasis is associated with an increased riskof stone formation.40

Biliary crystals

Occasionally, echogenic bile persists even with nor-mal gallbladder function (Fig. 3.45). The signifi-cance of this is unclear. It has been suggested thatthere is a spectrum of biliary disease in which gall-bladder dysmotility and subsequent saturation ofthe bile lead to the formation of crystals in the bileand also in the gallbladder wall, leading eventuallyto stone formation.41 Pain and biliary colic may bepresent prior to stone formation and the presenceof echogenic bile seems to correlate with thepresence of biliary crystals.42

Biliary crystals, or ‘microlithiasis’ (usually cal-cium bilirubinate granules) have a strong associa-tion with acute pancreatitis43 and its presence inpatients who do not have gallstones is thereforehighly significant.

Obstructive causes of biliary stasis

Pathological bile stasis in the gallbladder is due toobstruction of the cystic duct (from a stone, forexample) and may be demonstrated in a normal-sized or dilated gallbladder. The bile becomes vis-

cous and hyperechoic. The biliary ducts remainnormal in calibre. Eventually the bile turns wateryand appears echo-free on ultrasound; this is knownas a mucocoele (see above) (Fig. 3.8).

Bile stasis within the ducts occurs either as aresult of prolonged and/or repetitive obstructionor as a result of cholestatic disease such as primarybiliary cirrhosis (PBC) (Chapter 4) or PSC. This canlead to cholangitis.

HaemobiliaBlood in the gallbladder can be the result of gas-trointestinal bleeding or other damage to the gall-bladder or bile duct wall, for example iatrogenictrauma from an endoscopic procedure.

The appearances depend upon the stage of evo-lution of the bleeding. Fresh blood appears as fine,low-level echoes. Blood clots appear as solid, non-shadowing structures and there may be hyper-echoic, linear strands.44

The history of trauma will allow the sonogra-pher to differentiate from other causes of haemo-bilia and echogenic bile, particularly thoseassociated with gallbladder inflammation, andthere may be other evidence of abdominal traumaon ultrasound such as a haemoperitoneum.

PneumobiliaAir in the biliary tree is usually iatrogenic and is fre-quently seen following procedures such as ERCP,sphincterotomy or biliary surgery. Although it doesnot usually persist, the air can remain in the biliarytree for months or even years and is not significant.

It is characterized by highly reflective linearechoes (Fig. 3.46), which follow the course of thebiliary ducts. The air usually casts a shadow whichis different from that of stones, often having rever-berative artefacts and being much less well-definedor clear. This shadowing obscures the lumen of theduct and can make evaluation of the hepaticparenchyma difficult.

Pneumobilia may also be present in emphyse-matous cholecystitis, an uncommon complicationof cholecystitis in which gas-forming bacteria arepresent in the gallbladder (see above), or in caseswhere a necrotic gallbladder has formed a chole-cystoenteric fistula.


Figure 3.45 Biliary crystals.

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Rarely, multiple biliary stones form within theducts throughout the liver and can be confusedwith the appearances of air in the ducts.

MALIGNANT BILIARY DISEASE

Primary gallbladder carcinomaCancer of the gallbladder is usually associated withgallstones and a history of cholecystitis. Most often,

the gallbladder lumen is occupied by a solid masswhich may have the appearance of a large polyp.The wall appears thickened and irregular and shad-owing from the stones may obscure it posteriorly. Abile-filled lumen may be absent, further complicat-ing the ultrasound diagnosis (Fig. 3.47). In a porce-lain gallbladder (calcification of the gallbladderwall), which is associated with gallbladder carci-noma, the shadowing usually obscures any lesion inthe lumen, making the detection of any lesion pres-ent almost impossible.

Particular risk factors for gallbladder carcinomainclude large stones, polyps of over 1 cm in size,porcelain gallbladder and, occasionally, choledochalcyst due to anomalous junction of the pancreatobil-iary ducts.8

The carcinoma itself is frequently asymptomaticin the early stages, and patients tend to presentwith symptoms relating to the stones. It is a highlymalignant lesion which quickly metastasizes to theliver and portal nodes and has a very poor progno-sis, with a curative surgical resection rate of around15–20%.

Doppler may assist in differentiating carcinomafrom other causes of gallbladder wall thickening,45

but further staging with CT is usually necessary.Ultrasound may also demonstrate local spread intothe adjacent liver.


Figure 3.46 Air in the biliary tree following surgery.Note the ‘reverberative’ shadow.

A B

Figure 3.47 Gallbladder carcinoma. (A) TS, containing stones, debris and irregular wall thickening. (B) A differentpatient, demonstrating a grossly thickened hypoechoic wall with a contracted lumen.

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CholangiocarcinomaThis is a malignant lesion arising in the wall of thebile duct (Fig. 3.48). It is obviously easier to rec-ognize from an ultrasound point of view when itoccurs in and obstructs the common duct, as thesubsequent dilatation outlines the proximal part ofthe tumour with bile. Cholangiocarcinoma mayoccur at any level along the biliary tree and is fre-quently multifocal.

A cholangiocarcinoma is referred to as a Klatskintumour when it involves the confluence of the rightand left hepatic ducts. These lesions are often diffi-cult to detect on both ultrasound and CT. They arefrequently isoechoic, and the only clue may be theproximal dilatation of the biliary ducts (Fig. 3.49).

Although rare, the incidence of cholangiocarci-noma seems to be increasing and it is strongly asso-ciated with PSC, a disease of the biliary ductswhich predominantly affects young men (seeabove).

Multifocal cholangiocarcinoma may spread to thesurrounding liver tissue and carries a very poorprognosis for long-term survival. In a liver whosetexture is already altered by diffuse disease it may bealmost impossible to identify these lesions beforethey become large. A pattern of dilated ducts distalto the lesion is a good clue (Figs 3.50 and 3.51).


Figure 3.48 The distal CBD has a thickened wall(arrowheads), and the lumen is filled with tumour at thelower end. (Gallbladder anterior.)

A B

Figure 3.49 Cholangiocarcinoma. (A) Irregular mass at the porta, causing biliary obstruction—a Klatskin tumour.(B) MRI of the same patient, confirming the mass at the porta.

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