axr made easy

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The abdominal radiograph is one of themost commonly requested images, and allmedical students should have a knowledgeof common radiological interpretations.

This article covers the radiology of normalfindings. Subsequent parts of the series willcover abnormal intraluminal gas, abnormalextraluminal gas, calcification, bone andsoft tissue abnormalities, and iatrogenic,accidental, and incidental objects.

The standard abdominal radiograph(AXR) taken is a supine projection: x raysare passed from front to back (anteroposte-rior projection) of a patient lying down onhis or her back. In some circumstances anerect AXR is requested: its advantage over asupine film is the visualisation of air-fluid lev-els. A decubitus film (patient lying on his orher side) is also of use in certain situations.

Although an AXR is a plain radiograph, ithas a radiation dose equivalent to 50 pos-teroanterior chest x rays or six months ofstandard background radiation.

As with any plain radiograph, only fivemain densities are seen, four of which arenatural: black for gas, white for calcifiedstructures, grey representing a host of softtissue with a slightly darker grey for fat (as itabsorbs slightly fewer x rays). Metallic objectsare seen as an intense bright white. The clar-ity of outlines of structures depends, there-fore, on the differences between thesedensities. On the chest radiograph, this iseasily shown by the contrast between lungand ribsblack air against the white calcium

containing bones. These differences aremuch less apparent on the AXR as moststructures are of similar densitymainly softtissue.

Technical featuresIt is important, as with any image, that thetechnical details of an AXR are assessed.The date the film was taken and the name,age, and sex of the patient are all worth not-ing. This ensures you are interpreting thecorrect film with the correct clinical infor-mation and it also may aid your interpreta-tion. You would be a little concerned if yousaw what appeared to be a calcified fibroidon an AXR when holding the notes of MrJohn Brown.

Next ask what type of AXR is it: supine,

erect, or decubitus? Unless specificallylabelled the film is taken to be supine.

The best way to appreciate normality is tolook at as many films as possible, with anawareness of anatomy in mind (fig 1).

Intraluminal gasBegin by looking at the amount and distri-bution of gas in the bowels (intraluminal

gas). There is considerable normal variationin distribution of bowel gas. On the erect

AXR, the gastric gas bubble in the leftupper quadrant of the film is a normal find-ing. Gas is also normally seen within the

large bowel, most notably the transversecolon and rectum (fig 2).

Important characteristicsof bowel loops tobear in mind are their size and distribution

(where they are situated in relation to otherstructures). Normal small bowel should meas-ure less than 3 cm in diameter, whereas nor-mal colon should measure less than 5 cm indiameter. Thediameter of thecaecummay be

greater,but ifit isgreater than9 cmit isabnor-mal. Large bowel should lie at the peripheryof the film, with small bowel distributed cen-trally. Small andlargebowel canalsobe distin-guished, most easily when dilated, by theirdifferent mucosal markings. Small bowel has

valvulae conniventes that transverse the fullwidth of the bowel; large bowel has haustrathat cross only part of the bowel wall (figs 3and 4). These features are important in thenext part of this series,whichconsidersabnor-mal intraluminal gas.Occasionally, fluid levelsin the smallbowelare a normal finding.Valvu-laeconniventes andhaustrafilms

Faecal matter in the bowel gives a mot-tled appearance (fig 5). This is seen as amixture of grey densities representing a gas-liquid-solid mixture.

Extraluminal gasGas outside the bowel lumen is invariablyabnormal. The largest volume of gas youmight see is likely to be under the rightdiaphragm: this occurs after a viscus has

Abdominal x rays made easy:

normal radiographs

Figure 1. Normal film

Figure 2. Rectal gas film

Figure 3. Valvulae conniventes

Understanding x ray films is something that all clinical students

should get to grips with. Starting out as a doctor, you will not need

to be an expert but you will need to know the basics. Ian Bickle

and Barry Kelly present the first part of a new series on interpreting

plain abdominal radiographs


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been perforated. This gas within the peri-toneal cavity is termed pneumoperitoneum.

Gas in the right upper quadrant withinthe biliary tree is a normal finding aftersphincterotomy or biliary surgery, but it canindicate the presence of a fistula between thebiliary tree and the gut.

Beware of gas in the portal vein, as this

can look very similar to biliary air. Gas in theportal vein is always pathological and fre-quently fatal. It occurs in ischaemic states,such as toxic megacolon, and it may beaccompanied by gas within the bowel wall(intramural gas).

CalcificationCalcium is visible in a variety of structures,both normal and abnormal, and becomesmore common with advancing age. How-ever, review the following areas in particu-lar for evidence of calcification: cartilage ofribs, blood vessels (chiefly the aortoiliac andsplanchnic arteries), pancreas, kidneys, theright upper abdominal quadrant for gall-bladder calculi, and the pelvis, which maycontain a variety of calcified structures,

most commonly phleboliths. Part 4 of thisseries is dedicated to calcification on AXR.

Soft tissues and boneA review of the soft tissues entails evaluatingthe outlines of the major abdominal organs.Observing these structures is made easier bythe fatty rim (properitoneal fat lines) sur-rounding them. In fact, the loss of these fatplanes may indicate an ongoing pathologicalprocess, such as peritonitis. Look at the sizeand position of the liver and spleen. Look atthe position and size of the kidneys, lateral tothe midline in the region of the T12-L2 verte-brae (a useful way of identifying vertebrae:the lowest one to give off a rib is T12 andserves as a reference point). The renal outlineis usually three to three and a half vertebralbodies in length. Also, look for the clear out-line of the psoas muscle shadow(s). Finally,try to identify the outline of the bladder, seenmore clearly if full, within the pelvis. The

appearance of what looks like a soft tissuemass in the region of the stomach is moreoften than not actually a gastric pseudotu-mour. This is a normal finding on the supinefilm and represents gastric fluid lying withinthe fundus (fig 6).

The assessment of bones entails evaluat-ing the spine and pelvis for evidence of bonypathology. Osteoarthritis frequently affects

the vertebral bodies, as well as the femoraland the acetabular components of the hipjoint. Pagets disease may also be identified,commonly along the iliopectineal lines ofthe pelvis. Your bone survey should alsocheck for fractures, especially subtle femoralneck fractures in elderly people. The spineand pelvis are also common locations formetastatic deposits. In the spine this is classi-cally seen as the absent pedicle.

ArtefactsYou should be able to identify man madestructures correctly. These may be iatro-

genic (put there by health professionals),accidental (put there by the patient orother), or projectional (lying in front of orbehind the abdomen but spuriously pro-jected within it on the AXR). Examples ofiatrogenic structures would be surgicalclips, an interuterine contraceptive device,renal or biliary stent, an endoluminal aorticstent, or inferior vena cava filter. Accidentalfindings include bullets or a per rectumobject. Projectional findings include pyjamabuttons, coins in pockets, or body piercings(see part 6 of the series).

Ian C Bicklefinal year medical student, QueensUniversity, [email protected]

Barry Kelly consultant radiologist Royal VictoriaHospital, Belfast

Next month: Abnormal intraluminal gas

Review points

Technical specifics of the radiograph

Amount and distribution of gas

Extraluminal gas

Calcification

Soft tissue outlines and bony struc-

tures

Iatrogenic, accidental, and incidentalobjects

Presenting the AXR

This is the supine abdominal radiograph

of a 42 year old women taken yesterday.

It is technically satisfactory. The amount

and distribution of gas within the bowel

is normal. There is no bowel dilatation.

There is no evidence of extraluminal air.

Soft tissue outlines of the psoas muscles

and kidneys are seen. The kidneys are

normal in size and shape. There are noapparent bony lesions or abnormal calci-

fication. Incidentally, sterilisation clips

can be seen within the pelvis indicating

previous gynaecological intervention.

Key to densities in AXRs

Blackgas

Whitecalcified structures

Greysoft tissues

Darker greyfat

Intense whitemetallic objects

Places to look for abnormal

extraluminal gas

Under the diaphragm

In the biliary system

Within the bowel wall

Figure 4. Haustra films Figure 5. Faecal mottling

Figure 6. Gastric pseudotumour


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On an abdominal radiograph, as with allplain film images, four densities can beseenwhite, grey, slightly darker grey, andblackrepresenting bone, soft tissue, fat,

and air. Metallic objects are seen as intensebright white. The abdominal radiograph isa representation of the abdominal visceraand bowel: the presence of gas in mostinstances is normal. Several medical andsurgical conditions, however, are recognis-able by an abnormal amount, distribution,or location of air on the radiograph. Abnor-mal gas can be (a) intraluminal, in the stom-ach, duodenum, and intestine, or (b)extraluminalthat is, elsewhere.

Large bowel obstruction andparalytic ileus

Most intraluminal gas is in the large intes-tine, which has the greatest luminal diame-ter of the intestinal tract. A diameter ofmore than 5 cm suggests a large bowelobstruction and would be considered abnor-mal (except in the caecum). As the intestineis a large long tube, any obstruction, eitherfrom within or by external compression,prevents the passage of faecal material andgas. Consequently, both will build up proxi-mal to the obstruction, causing dilation.

Unless the ileocaecal valve is incompetentthis gas-faecal material mix will be containedentirely within the large bowel. With time,the passage of a motion will empty any faecalmaterial and gas distal to the blockage. Thisgives the appearance of a cut off point onthe radiograph (fig 1). This is an importantsign to appreciate, as it is indicative of amechanical large bowel obstruction.

The large bowel can also dilate with para-lytic ileus. In this condition, the bowel is ady-namic (not undergoing normal peristalsis).This allows gaswhich everyone swallowsnormallyto accumulate in the bowel, butimportantly this air is contained within boththe small and large bowel (fig 2). There is alsono evidence of a cut off, as it is bowel peri-stalsis, not obstruction, that is the problem.

Two other pertinent radiological signshelp confirm that it is the large bowel that isobstructed. Firstly, large bowel has distincttransverse bands, termed haustra. These donot cross the full diameter of the bowel,unlike the transverse valvulae conniventes of

the small bowel. These can both be seen onplain radiograph.1 Secondly, large bowel isfound at the radiographs periphery asopposed to the small bowel loops, whichtake up central positions. This has beenreferred to as a picture frame of largebowel and the picture of small bowelwithin the frame.

Small bowel obstructionIn small bowel obstruction, dilated smallbowel loops are seen centrally on the radi-ograph. The valvulae conniventes shouldbe visible across the whole width of thisdilated bowel. The dilated bowel diameteris greater than 3 cm but usually less than 5cm. There are likely to be several dilatedbowel loops. The number of small bowelloops gives an indication of the level atwhich the obstruction within the smallbowel has occurred: the higher theobstruction, the fewer the number ofloops seen. Unlike large bowel obstruction(table), no gas should be seen within the

large bowel (fig 3).So far we have considered supine abdom-inal radiographs. An erect film may showfurther evidence of small bowel obstruction:fluid levels, indicating an air-fluid interface.An erect film tends to show multiple small

fluid levels, a stepladder appearance (fig 4).

VolvulusA volvulus is the twisting of bowel about itsmesentery, causing intestinal obstruction.The two most common sites are the sigmoidand the caecum. With a sigmoid volvulus, anextremely dilated loop of sigmoid bowelforms two large compartments which looklike a coffee bean (hence the name of thesign). This single loop usually fills most of thelower abdominal radiograph. On erectabdominal radiographs a fluid level may benoted.

Abdominal x rays made easy:abnormal intraluminal gas

Comparison of large and small bowel

obstruction features

Feature Obstruction

Small Large

bowel bowel

Bowel diameter (cm) >3 and 5

Position of loops Central Peripheral

Number of loops Many Few

Fluid levels Many, short Few, long

(on erect film)

Bowel markings Valvaulae Haustra

(all the way across) (partially across)

Large bowel gas No Yes

Fig 1. Large bowel obstruction

Got a blockage in your learning? Let Ian Bickle and Barry Kelly

help by explaining bowel obstruction and other causes of abnormal

intestinal gas, in the second part of our series on abdominal

radiographs

Fig 2. Paralytic ileus


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In caecal volvulus, the caecum is displacedto the upper left abdominal quadrant fromits normal location (the right lower quad-rant). This leaves the area empty so the termempty caecum is used. The volvulus usuallyconsists of a single loop, again showing afluid level on an erect radiograph. Distal tothe volvulus the large bowel is empty.

Toxic megacolon, acute

pancreatitis, duodenalobstruction, and meteorismToxic megacolon, seen in inflammatorybowel disease (especially ulcerative colitis),has an associated risk of bowel perforation.It is seen as grossly dilated large bowel, typ-ically the transverse colon, with thumbprinting evident (fig 5).

In acute pancreatitis a small sentinel loop(a collection of intraluminal gas) of bowelmay be seen: the inflamed pancreasparalysing the adjacent bowel, making it ady-namic. Duodenal obstruction, congenital oracquired, gives the appearance of two gasbubbles, one in the duodenum and the nor-mal gastric air bubble; this is termed thedouble bubble sign.

Meteorism (excessive swallowed air) isparticularly common in crying childrenand hyperventilating adults. Althoughthere are prominent bowel loops, there isno cut off point: the bowel has beenlikened to crazy paving (fig 6).


Barry Kelly consultant radiologist, Royal VictoriaHospital, Belfast

Next month: Abnormal extraluminal gas

1 Bickle IC, Kelly B. Abdominal x rays made easy: nor-mal radiographs. studentBMJ2002;10:102-3. (April.)

Fig 4. Small bowel obstructionerect

Fig 5. Toxic megacolon Fig 6. Meteorism

Fig 3. Small bowel obstructionsupine


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This month, in the third part of

our series on abdominal

radiographs, Ian Bickle and

Barry Kelly look at identifying

abnormal extraluminal gas on

plain abdominal films

Extraluminal gas is gas outside the sealedgastrointestinal tract.

PneumoperitoneumA most important and potentially devastat-ing finding is that of free intraperitonealgas, which is known as pneumoperitoneum.

Emergency surgical intervention is likely tobe necessary, as pneumoperitoneum usu-ally indicates a perforated viscus. The sup-plementary plain radiograph should be an

erect chest radiograph that visualises gascollecting beneath the diaphragm. Depend-ing on the volume of gas in the peritoneum,it may be apparent under one or both

hemidiaphragms. As you may recall fromthe first part of the series (normal radi-ographs) a gastric air (gas) bubble is usu-ally seen in the left hypochondrium on theerect film. This can make distinguishingfree air on this side problematic. For thisreason, identification of free gas on the

right side is more straightforward. The air istrapped between the underside of thediaphragm and the upper surface of theliver (fig 1). A small volume of gas has acrescentic appearance.

Should a supine abdominal radiographbe the only film availableif, for example,the patient is too ill to undergo an erectchest radiographthere are radiological

Abdominal x rays made easy:

abnormal extraluminal gas

Conditions causing extraluminal

air

Perforated abdominal viscus

Abscesses (subphrenic and other)

Biliary fistula

Cholangitis

Pneumatosis coli

Necrotising enterocolitis

Portal pyaemia

Fig 1. Gross pneumoperitoneum with free air under both hemidiaphragms. In additionthere is a large dark egg shape projected through the heart. This is a large, fixed, hiatusherniaan incidental finding, but one which shows an abnormal air collection

Fig 2. A subtle pneumoperitoneum

Fig 3. Falciform ligament (left) and Riglerssign (right) dark triangles outlined by the

bowel wall serosa

Falciform

ligament

Riglers sign

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signs that help identify free gas on theradiograph. The falciform ligament sign isseen when free air outlines the falciform lig-

ament, identified as a thin straight line start-ing in the right upper quadrant, where itoriginates, and ending near the umbilicus,where it terminates (fig 2). In Riglers sign,gas can be seen on both sides of the bowelwall (fig 3). This makes the serosal surfaceof the bowel easily visible.

Chilaiditis syndromeChilaiditis syndrome is an important nor-mal variant on the erect chest radiograph,which must be distinguished from patho-logical free gas under the diaphragm. Inthis phenomenon, gas is seen between the

hemidiaphragm and the liver or spleen (fig4). On close and careful observation thisshould be identified as gas filled largebowel, most likely transverse colon (appar-ent, as haustra are seen within the gas filledstructure). This gas is still contained in thebowel loop.

Subphrenic abscessThis is a localised collection of free gas andfluid, which usually forms under the righthemidiaphragm, above the solid liver. Thisgas collection usually occurs above the 11thrib (fig 5).

Biliary gasOn the plain abdominal x ray film, gas isnot normally identified in the biliary sys-

tem, either intra- or extrahepatic. There are,however, situations when gas might be seenas branching tree-like streaks of black

projected in the liver shadow. After endo-scopic retrograde cholangiopancreatogra-phy with sphincterotomy, gas may travelfrom the duodenum into the biliary tree asthe sphincter of Oddi in the second part ofthe duodenum is incompetent. Similarly,after a gallstone has been passed, thesphincter may become dilated. Biliary fistu-

las are less common but may develop with agallstone ileus. Fistulation between the gall-bladder and adjacent bowel allows a routefor gas into the biliary system. The finalaetiology is cholangitis. If the biliary ductsare infected with gas forming organisms,gas will be produced, and contained, in theducts, effectively creating a negative con-trast to the surrounding soft tissue of theliver.

Miscellaneous causesThe final causes of extraluminal gas areconditions where gas has escaped from thelumen of the gastrointestinal tract butremains within the bowel wall; this is known

as intramural gas. This gas may migrate tothe portal vein and is effectively an antemortem sign, except in the case of neo-natal necrotising enterocolitis.

Necrotising enterocolitis is a conditionseen in premature babies when gas leaksinto the bowel wall.

In bowel wall infarction, abscesses mayform, which produce gas contained in thebowel wall.

Pneumatosis coli, a condition whereblebs of gas form on the bowel wall, is ofobscure aetiology and makes the bowelwall look like bubble wrap. These blebsmay rupture to produce a pneumoperi-toneum.

Ian C Bicklefinal year medical student, QueensUniversity, Belfast

Barry Kelly consultant [email protected], Royal Victoria Hospital, Belfast

Next month: Calcification

Fig 4. Chilaiditis sign

Fig 5. Subphrenic abscess


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As outlined earlier in the series a smallnumber of densities may be seen on plainradiographs. The most radio-opaque(brightest) of any natural substance is cal-cium, which appears white. The reasoncalcium shows the greatest radio-opacityis that it obstructs xrays more than anyother natural substance. Consequently,fewer of those xrays reach the xray plate,and the film appears white.

Iatrogenic or artefactual metallicobjects appear even brighter white (thiswill be discussed in the final part of thisseries). The vast majority of calcium iscontained in the bonesa normal,expected location (bony abnormalities willbe covered in the next part of this series).

The incidence of physiological calcif i-cation of normal anatomical structuresincreases with age and reflects that cal-cium is deposited over time.

Calcium can be seen in normal andabnormal structures. Abnormal calcifica-tion in some cases merely indicates under-lying pathology whereas in others the

calcification is the pathology.

Calcification of normalstructures (box 1)Evaluation of the abdominal radiographmight start at the top, working down the

film. The film should include the loweranterior ribs. As you will recall, towardsthe midline anteriorly, a rib changes frombone to cartilage and is termed costal car-tilage. The cartilage of ribs one to sevenarticulates with the sternum whereas ribseight to 10 indirectly connect to the ster-num by three costal cartilages, each ofwhich is connected to the one immedi-ately adjacent to it (ribs 11 and 12 arefloating). This cartilage can calcify, whichis termed costocalcinosis. Althoughappearing strikingly abnormal, it is harm-less and usually age related (fig 1).

Further down, mesenteric lymph nodes

may calcify and appear as oval, smooth,outlined structures (fig 2). These can beconfused with small kidney stones, espe-cially in a patient without previous filmswho presents with abdominal pain. Aresuch incidental harmless calcified nodes

responsible for the pain or are renalcalculi This diagnostic dilemma may be

solved by the exact location. If due calcifica-tion is identified along the urinary pathway(typically along the line of the transverseprocesses of the vertebral bodies) an intra-venous urogram to compare against a plaincontrol film may be necessary for a decisivediagnosis. Alternatively, unenhanced com-puted tomography can be used. Also con-tained in the pelvis is the pelvic phlebolith,seen as a small, smooth, round, white opac-ity. Phleboliths are small areas of calcifica-tion in a vein. They may be difficult todifferentiate from small kidney stones.

The final calcification in this section isfound only in men. This is calcium that

collects in the ageing prostate gland and istherefore observed low down in the pelvicbrim. Prostate calcification may also occurin cancerous tissue.

Calcification indicatingpathology (box 2)

PancreasThe pancreas lies at the level of T9-T12vertebrae. Calcification of the pancreas isusually found in chronic pancreatitis,although there are some rarer causes. Ifcalcification is extensive, the full outline of

the pancreas may be observed, mostly onthe left side, but may cross over the mid-line. This speckled calcification occurson the network of ducts within the pan-creatic tissue where most of the calcium isdeposited (fig 3).

Renal calcificationBetween the T12-L2 vertebral region,nephrocalcinosis may be identified. Thisis calcification of the renal parenchymaltissue (fig 4). This is indicative of renalpathology, which includes hyperparathy-roidism, renal tubular acidosis, and

medullary sponge kidney.

Vascular calcificationPerhaps the most striking calcification is inthe blood vessels, most notably the arter-ies. The whole vessel(s) may be exquisitely

Abdominalxrays made easy: calcification

Ian Bickle and Barry Kelly return after a month off with the fourth part in their series on reading plainabdominalxray films

Fig 1

Fig 2

Box 2: Abnormal structures that

contain calcium

Calcium indicates pathology Pancreas

Renal parenchymal tissue

Blood vessels and vascular aneurysms

Gallbladder fibroids (leiomyoma)

Calcium is pathology

Biliary calculi

Renal calculi

Appendicolith

Bladder calculi

Teratoma

Box 1: Normal structures that

calcify

Costal cartilage

Mesenteric lymph nodes

Pelvic vein clots (phlebolith)

Prostate gland

Fig 3


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outlined by calcium (fig 5). A great deal ofcalcification may be indicative of a wide-spread atheromatous process within thearteries, especially in diabetes.

In the infrarenal arterial region, belowthe second lumbar vertebrae, abdominal

aortic aneurysms are typically located.Over time, as the atheromatous materialis laid down in the lumen, calcium may bedeposited. This may appear on an abdom-inal radiograph, and can be identified,often incidentally, by giving a rough indi-cation of the internal diameter. Anabdominal ultrasound scan should imme-diately follow for accurate assessment, andto determine the timing of surgery orobservational follow up.

Gynaecological calcificationThe final structure in this section is foundonly in womenfibroids. These can

become calcified and appear as roundedstructures of varying size and location inthe pelvis (fig 6).

Pathological calcificationThe final section on calcif ication onabdominal xray film refers to pathologi-cal calcification. This almost exclusivelymanifests as calculi in various locations.Calculi may be asymptomatic.

Biliary calculiBiliary calculi are commonly referred toas gallstones. Plain abdominal x ray film

in itself is poor at identifying these calculiand detects only 10-20%. Ultrasound isthe gold standard for first line imaging. Aplain abdominal radiograph is often theinitial investigation in patients withabdominal pain and may identify these

laminated, faceted, often multiple, radio-opacities in the right upper quadrant ofthe radiograph (fig 7). Very rarely a largecalculus may erode into the gallbladderwall, creating a fistula to the adjacentsmall bowel. This calculus may then pass

along the intestinal tract until it cannottravel any further, usually in the distalileum a little proximal to the ileocaecalvalve, and cause an obstruction of the

small bowel (see part 2 of this series). Gasmay also be seen in the biliary tree on the

abdominal radiograph (see part 3 of thisseries). This phenomenon is termed agallstone ileus. In the right upper quad-rant the wall of the gallbladder itself may

Fig 5

Fig 6

Fig 4

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become calcif ied after repeat incidencesof cholecystitisthis is termed a porcelaingallbladder (fig 8). A significant relation

(20%) exists between this and the devel-opment of gallbladder malignancy.

Renal calculiThese are much more commonly identi-fied on the abdominal radiograph; up to80% are visible. The variable detection is a

result of the different degree of radio-opacity, which, in turn, is dependent onthe composition of the calculus. Renal cal-culi may also vary greatly in size, thelargest being a staghorn calculus. Theyare, however, usually smaller but found onthe well defined pathway of the urinarytract and seen by looking down the trans-

verse processes of the vertebrae, acrossthe sacroiliac joint to the level of the

ischial spine. It is also worth noting thatcalculi tend to obstruct at some favouredlocations, which include the pelviureteric,brim of the pelvis, and vesicouretericjunctions.

Appendix and bladderIn the region of the right iliac fossa, asmall calcified, round radio-opacity maywell be an appendicolith . These are seenin 15% of appendicitis. In the pelvicregion of the abdominal xray film bladdercalculi may be seen, but less commonlythan biliary or renal calculi. Bladderstones are usually quite large and oftenmultiple. Calcification of a bladder

tumour may also occur.A final mention goes to the teratoma, a

type of tumour derived from the primitivegerm cell lines, which occurs in theovaries and testes. In some instances teeth

may develop from the ectoderm layer; asthey are highly calcified they will appearon the radiograph and are easily identi-fied as they look tooth shaped (fig 9).

The next part of this series looks atbones and soft tissue findings on abdomi-nal xray films.


Barry Kelly consultant radiologist, Royal VictoriaHospital, Belfast

Fig 8

Fig 9

Fig 7


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Often, little attention is paid to bones andsoft tissues when reviewing an abdominal xray film. However, careful inspection mayfind new, associated, or longstanding con-comitant pathology. With concomitantpathology two abnormalities are identifiedbut have no direct associationfor example,an abdominal aortic aneurysm and a fracture

of the femoral neck. So including bone andsoft tissues as part of a systematic reviewensures that no significant findings are over-looked (box 1).Lets begin by reminding ourselves of the

bones and soft tissues shown on an abdomi-nal xray film.

AnatomyBones include the lower ribs and their artic-ulations, the lower thoracic and the lumbarspine, the bony pelvis, and the proximalfemora. Soft tissues include the abdominalviscera and the surrounding muscle andsoft tissues that envelop the lower trunk.

Pathology of the bone and soft tissues canbe identified on abdominal x ray film forthree main reasons: it may be new pathol-ogy, causing the symptoms that precipitatedthe abdominal xray film, associated pathol-ogy, or concomitant pathology.

BonesBony pathology may be divided into localand generalised disease (box 2).

Generalised bone pathology

Osteoporosis can be identified as osteo-penia when at least 15% of bone mass has

been lost. It is commonly seen in the verte-bral bodies, often coincidentally, in other-wise symptomless, postmenopausal womenwho are being investigated for other rea-sons. Its manifestation may also be as a ver-tebral wedge (crush) fracture, leading toscoliosis and kyphosis see fig 1 (also see thismonths Minerva picture, p 352).

Similarly, Pagets disease affects almostexclusively elderly people. In the spine, thereis usually involvement of the vertebral bodywith coarsening and thickening of the tra-beculae, bony enlargement, and sometimesan ivory vertebra (uniformly white, withoutcontours). Another common site is the

ileopectineal line of the pelvis (fig 1).

Localised bone pathologyLocalised Pagets disease may be difficult todistinguish from sclerotic metastases. Auseful clue is that Pagets disease typicallyextends to the end of the bone whereasmetastases are more randomly distributed.Sclerotic metastases are typical of prostaticcarcinoma or lymphoma. Metastases are,

however, more commonly lytic. These are

destructive lesions; seen as areas of bonyradiolucency, which appear as dark areaswithin a bone.

Abdominalxrays made easy: bones and soft

tissuesIn the fifth article in their series on how to read plain abdominal x ray films, Ian Bickle and Barry Kelly

discuss inspecting bones and soft tissues and interpreting the findings

Box 1: Interpreting an abdominal

x ray film (a reminder)

Technical specifics

Amount and distribution ofintraluminal gas

Extraluminal gas Calcification

Bone and soft tissues

Iatrogenic, accidental, and incidentalobjects

Box 2: Bony pathology

Generalised osteoporosis (seen asosteopenia)

Pagets disease

Metastatic deposits (sclerotic and lytic)

OsteoarthritisFractures

Ankylosing spondylitis

Box 3: Radiographic features of

osteoarthritis of the hip

Loss of joint space

Osteophyte formation

Subchondral sclerosis

Bone cysts

Fig 2: Bamboo spine

Fig 1: Scoliosis and kyphosis


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The term lucent or lucency is used todescribe a focal area of bony osteopeniaforexample, a bone cyst. The term lytic how-ever implies a lucent lesion that appearsinfiltrativefor example, metastases orosteomyelitis. A lytic bony metastasis classi-cally presents as an absent pedicle on theanterior view, the metastasis having

destroyed the pedicle.Metastases are one of the causes of frac-tures seen on abdominal xray film. Fracturesmay be recent (and may be the immediatecause for the assessment) or old. Vertebral,femoral neck, rib, and pelvic fractures feature

on the abdominal xray film and may haverelevance to other features on the film.

Primary bone disease seen on abdominalx ray film is usually a coincidental finding,often already recognised and cared for byother hospital specialists. In elderly people,osteoarthritis of both the spine and thefemoral head are found often. Osteoarthritis

of the femoral head has several well recog-nised radiographic features (box 3).In younger patients, ankylosing spondyli-

tis may affect the spine and the pelvis. Fusionof the sacroiliac joints precedes spinalinvolvement. This latter feature is described

classically on radiographs as a bamboospine, with evidence of syndosmophyte for

mation and calcification of the longitudinalspine ligaments (see Figs 2 and 3)

Soft tissuesThe yield of posit ive radiographic findingsinvolving the soft tissues is less than forbone. Calcif ication involving soft tissuestructures was discussed in an earlier partof this series.1Alteration in size and shapeof solid organs, such as the kidneys (box4), liver, and spleen can be observed, asmay the loss of their properitoneal fatlines. Furthermore, the loss of the psoasmuscle shadows may indicate intraperi-toneal disease (see Fig 4)

Ian Bicklepreregistration house of ficer, Barry Kellyconsultant radiologist, Royal Victoria Hospital, [email protected]

1 Bickle I, Kelly B. Abdominal x rays made easy:calcification. studentBMJ2002;10:272-4. (August.)

Box 4: An illustrated case

Renal carcinoma with bony metastases

A school caretaker aged 58 yearspresented complaining of a three weekhistory of blood in his urine and loin pain.He also admitted to noting a drop in hisweight in the region of 5 kg over the pastthree months. He had experienced norecent trauma or previous medical historyof note.

On examination, a mass was palpablein the right loin with an area of overlyingtenderness. A 2 cm hepatic margin wasalso noted. The rest of the examination didnot show any abnormal findings. Thecasualty officer had ordered a supineabdominal x ray film

During a quiet moment you inspect the

radiograph and note the presence of anirregular tissue mass measuring 13 X 10cm on the right side, lateral to the vertebralcolumn. Some adjacent displacement ofbowel is visible. Continuing to inspect thefilm fully you notice a lytic lesion in theregion of the T12 vertebra that seems tohave destroyed the pedicle.

You are suspicious of a sinister renalmass so request an urgent ultrasound scanof the abdomen. The radiologistsubsequently phones the ward and reportsthe presence of a solid, irregular mass inthe right kidney, which extends to the rightrenal vein, reducing its patency. A

radiologically guided biopsy confirmedyour suspicions, diagnosing a renal cellcarcinoma.Fig 4: Absent left psoas muscle shadow

Fig 3: Fusion of sacroiliac joints


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In the final part of our series we will focuson iatrogenic, accidental, and incidentalobjects seen on abdominal x ray films.These artefacts may be placed inside thebody (internal) or be about the person(external). Internal objects may have beenplaced with intention by a health profes-sional or temporarily by the individual con-cerned. Intentionally placed internalobjects may have required surgery or beeninserted through one of the bodys naturalorifices (mouth, vagina, anus). Incidental

objects are those that become projected onto the radiograph.

Iatrogenic objectsThese are placed intentionally by a healthprofessional.

A wide range of medical devices appearon the abdominal x ray film, and many havebeen placed by radiologists themselves. Onsome occasions a radiographs sole purposeis to confirm the position of an object, such

as a tube device, most commonly the naso-gastric tube (figure 1). These are the most

commonly found iatrogenic objects, andtheir position is sometimes confirmed by achest x ray film.

Other devices may be in the vascular,hepatopancreatobiliary, gastrointestinal, and

Abdominal x rays made easy: iatrogenic, accidental,

and incidental objectsIn the final part of this series, Ian Bickle and Barry Kelly look at some of the more unusual findings on

an abdominal x ray film

Internal objects

Iatrogenic

Biliary or vascular stent

intrauterine coil devices

Sterilisation clips

Surgical clips

Greenfield filter (inside inferior venacava)

Percutaneous endoscopic gastrostomytube

Nasogastric tube

Accidental

Swallowed objects: razor blades,batteries, paper clips

Objects placed inside rectum orvagina: caps, bottles, vibrator

External objects

Incidental

Stoma ring

Objects in clothing: coins, keys, comb

Objects on clothing: buttons, clips,zips

Figure 1 (left) nasogastric tube clips fprrecent surgery and figure 2 (above)intruterine coil device in situ


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genitourinary systems.Evidence of vascular intervention may be

seen in the form of arterial stents and theplacement of filters in the venous systemfor

example, the Greenfield filter placed in theinferior vena cava, which is used to preventrecurrent pulmonary emboli.

The hepatopancreatobiliary system is alsoroutinely stented, often for palliative relief ofobstructive jaundice secondary to neoplasm.The stenting is performed either by radio-logical percutaneous transhepatic cholan-giography (PTC) or by endoscopicretrograde cholangiopancreatography(ERCP).

A percutaneous endoscopic gastrostomy(PEG) tube may also be seen on an abdomi-nal x ray film.

In women, intrauterine coil devices andsterilisation clips are readily seen in the

lower half of the abdominal x ray film withinthe pelvis (figure 2). Tampons may alsoappear as tubular gaseous densities withinthe pelvis and should not be confused withanything more sinister.

Incidental objectsThese objects seen on an abdominal x rayfilms usually do not affect the wellbeing ofthe patient. These objects are externa;, theyare either attached to the patients body orcontained on or inside the patients clothes.Attached objects may indicate medical con-ditions, such as a stoma ring (figure 3) or

represent body art, such as a naval ring (fig-ure 4). Other incidental objects can be partof peoples clothing, such as buttons, zips,clips, or brooches.

Alternatively, the projected objects areinside a patients clothingin the case of theabdominal x ray film, usually a trouserpocket that has not be emptied before a filmis taken. These can be metallic objects suchas coins, paper clips, and keys, or otherdense objects such as a comb.

Accidental objectsThese are objects that have been placed inthe body by the individual concerned. The

object then either remains in place andbecomes immovable or progresses furtherthrough the gastrointestinal tract andbecomes lodged. Distinction can be madebetween objects swallowed or objectsplaced in the rectal or vaginal orifices. Onoccasion these objects may be retained for-eign bodies, such as a knife after a stabbing(figure 5).

Swallowed objects may be ingested inten-tionally or by misfortune. They usually travelthrough the gastrointestinal tract, but onoccasion they become lodged. Razor blades,batteries, coins, paper clips, and small toysare just a few of the potential objects (figure6). Three chief groups of patients fall intothis categorypatients with psychiatric illhealth, children, and drug smugglers.

Per rectum (PR) objects, such as bottles,

vibrators, and light bulbs, are almost alwaysplaced inside the rectum for sexual pur-poses, only to become retained, requiringmedical attention for extraction (figure 7).

Ian Bicklepreregistration house officer, Barry Kellyconsultant radiologist, Royal Victoria Hospital, Belfast,

Thanks to Brian Grant, senior radiographer,Accident and Emergency Department, RoyalVictoria Hospital, Belfast

Figure 3 (top): stoma ring, figure 4 (above):navel ring, and figure 5 (below): a knife inthe abdomen

Figure 6: swallowed objects (3 cigarettelighters)

Figure 7: a bottle per rectum

axr made easy

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