Urinary Tract Calculus

5th Year Group 5

Tutorial and case presentation

CONTENT

Aetiopathogenesis Presentation and differential diagnosis Imaging

X-ray KUB X-ray Intravenous pyelogram/urogram (IVP=IVU)

Ultrasound (KUB) Abdomen CT scan MRI

AETIOPATHOGENESIS

Urolithiasis = nephrolithiasis Presence of abnormally high calcium excretion

exceeding lymphatic capacity, microaggregates of calcium (present in the normal kidney) occur in the medulla, increase in size, migrate toward caliceal epithelium, and rupture into calyces to form calculi.

Mineral composition Frequency (%) Opacity

Calcium stones(salts, oxalate, phosphate, urate)

70-80 +++

Struvite stones 15-20 ++

Uric acid (radiolucent) 5-10 -

Cystine (mildly opaque) 1-3 +

Xanthine (nonopaque) Extremely rare -

PRESENTATION AND DIFFERENTIAL DIAGNOSIS

Stone location Common symptoms

Kidney Vague flank pain, hematuria

Proximal ureter Renal colic, flank pain, upper abdominal pain

Middle section of ureter Renal colic, anterior abdominal pain, flank pain

Distal ureter Renal colic, dysuria, urinary frequency, anterior abdominal pain, flank pain

Renal causes Non renal causes

Ureteric calculusRenal calculusPelvi-ureteric junction obstructionAcute pyelonephritisUreteric strictureTCC of ureter cause obstructionClot colic

AppendicitisTorsion or hemorrhage of ovarian cystCholedocholithiasisDiverticulitisIBDPancreatitis

ACUTE FLANK PAIN

IMAGING (ROLES IN NEPHROLITHIASIS) To confirm the diagnosis. To help establish both the possible

cause and consequences of the stone. Primary finding – calcification. Secondary finding (evidence of obstruction)– dilatation,

perinephric stranding, renal enlargement, renal hypodensity.

To help monitoring and evaluate the progression of disease before and after the treatment.

IMAGING (MODALITIES)Modality

Sensitivity

Specificity

Advantages Limitations

Ultrasonography

19 97 Accessible, inexpensive, safe, radiolucent stone in the kidney visible.

Limited accuracy for renal stones, ureteral stones not seen, poor anatomic information, reproducibility of size measurement limited, fragmentation not readily appreciated.

Plain film radiography

45-59 71-77 Accessible, inexpensive, good reproducibility for size measurement, fragmentation readily assessed, good for follow up of ureteral calculi.

Radiation, bowel gas may limit visibility, no information about caliceal anatomy, radiolucent stones not seen.

Modality Sensitivity

Specificity

Advantages Limitations

Intravenous urography (IVU)

64-87 92-94 Accessible, excellent anatomic definition.

Radiation, requires bowel preparation and use of contrast media, poor visualization of nongenitourinary conditions, delayed images required in high-grade obstruction, radiolucent stones may not be seen.

Non-contrast helical CT

95-100 94-96 Very high diagnostic accuracy, all stones visible (except indinavir), caliceal anatomy may be reconstructed, provide indirect signs degree of obstruction, information on genitourinary conditions, ability to measure stone density.

Radiation dose higher than that of IVU, limited availability, relatively expensive.

KUB X-RAY

Normal KUB. Note that portions of the normal renal contours (arrows) are visible and should be evaluated. No abnormal calcifications, soft tissue densities, or bony lesions are evident.

Bilateral staghorn calculi and subchondral bone resorption at the ileal aspect of the

sacroiliac joint.

©1999 by Radiological Society of North America

KUB shows two dense 1-cm calcifications (arrows) projecting over the mid-portion of the left kidney consistent with nephrolithiasis

Multiple bladder calculi

Phleboliths in the gonadal vein mimicking ureteral stones.

(a) Plain radiograph shows three 3-mm areas of high opacity at the level of the right midureter (arrows).

(b) Urogram shows these areas of high opacity (arrows) to be adjacent to but outside the ureter, indicating that they represent phleboliths in the gonadal vein.

Fallopian tube bands. Plain radiograph demonstrates a 3-mm Silastic fallopian tube band used for tubal ligation mimicking a ureteral stone in the left pelvis (arrow).

A second band is seen en face in the right pelvis (arrowhead).

INTRAVENOUS PYELOGRAM (IVP)

To prove that an opacity seen on plain films lies within the urinary tract.

To diagnose lucent calculi not seen on plain films.

To identify other causes of renal colic, as above, and guide further actions.

Overlying stool can obscure important detail on an intravenous pyelogram and therefore a mild bowel preparation of clear liquids and laxatives before an elective study is recommended. (not suitable for urgent examination)

The study should always begin with a scout KUB. This has several purposes including detection of calcifications (which may be obscured after contrast material is injected), assurance of proper technique (patient positioning, exposure parameters) prior to contrast administration, and exclusion of contraindications to the study (retained barium, etc.).

The scout film should encompass the area from the adrenals to the symphysis pubis, and sometimes more than one film may be required.

Intravenously injected iodinated contrast is excreted primarily by glomerular filtration in the kidney, opacifying the urinary tract as it progresses from the kidney through the ureter and to the bladder.

Capturing this sequential "opacification" on radiographs is the fundamental basis of the IVU.

There are many variations in the filming sequence for the urogram that are acceptable as long as it optimizes visualization of specific anatomy of the urinary tract during maximum contrast opacification.

Normal pyelogram. Note the delicate cup-shaped appearance of the calyces and the relative symmetry of the renal pelvis with no evidence of dilation or mass effect.

Normal bladder. Note the location of the bladder just above the pubic symphysis, as well as its smooth contour. No filling defects should be seen.

ULTRASOUND Ultrasound imaging is useful as it gives details about the

presence of hydroneprosis (swelling of the kidney—suggesting the stone is blocking the outflow of urine).It can also be used to detect stones during pregnancy when x-rays or CT are discouraged. Radiolucent stones may show up on ultrasound however they are also typically seen on CT scans.

Some recommend that US be used as the primary diagnostic technique with CT being reserved for those with negative US result and continued suspicion of a kidney stone. This is due to its lesser cost and lack of radiation exposure.

The ureters are not normally seen on ultrasound due to obscuring overlying tissue and their small size. Evidence of their patency may be verified by Doppler detection of urine rapidly entering the bladder from the distal ureters.

The bladder is seen as a rounded or oval anechoic (fluid) structure in the pelvis. The bladder may demonstrate mass lesions, such as transitional cell carcinoma, or stones. The urethra is not typically seen on an ultrasound image although urethral diverticula may occasionally be demonstrated.

Normal renal ultrasound: long axis view and drawing. Note the smooth contour of the kidney. The rounded to cone-shaped medullary pyramids are hypoechoic to the cortex and should not be mistaken for a mass or dilated collecting system. The renal cortex should be similar to or slightly hypoechoic compared with liver. In addition, notice the hyperechoic fat of the renal sinus—the central echo complex.

CT-SCAN (NCHCT)

Goal of modern imaging is to provide accurate information concerning the presence, size, and precise location of a renal or ureteral stone, in addition to delineating the intracaliceal anatomy.

Due to its many advantages, NCHCT is currently the imaging method of choice in the identification and evaluation of urinary tract calculi, although it is not always available, and concerns about radiation dose exist.

Noncontrast helical CT scan of the abdomen demonstrating a stone at the right ureterovesical junction

Normal CT image of the distal ureters and urinary bladder. Although contrast has been administered, it has not yet reached the bladder. Note that despite their small size and lack of contrast, the ureters can be identified (arrows) within the retroperitoneal fat. The right ureter is seen near its point of entrance to the bladder. The bladder contains water density urine and a thin, smooth wall can be delineated.

Normal CT showing the distal ureters and urinary bladder opacified with IV contrast. After a 5-minute delay, the distal ureters (arrowheads) and bladder are easily identified. Delayed images may be necessary to evaluate the ureter or bladder in certain circumstances.

MAGNETIC RESONANCE UROGRAPHY (MRU)

Limited to patients in whom other investigations are contraindicated, for example pregnant woman.

MR-urography and CT-urography provide refined imaging of the upper urinary tact which is not possible with conventional I.V Urography.

Utilising heavily T2-weighted (T2W) pulse sequences can easily depict a dilated ureter and demonstrate the level of obstruction without the use of ionising radiation and contrast material.

Ureteric stones are seen as filling defects in the ureter on MRU.

T2-weighted MR-urograms have proved excellent in visualizing dilated urinary tact even in non excreting kidneys.

T1-weighted excretory MR-urogram provides impressive urograms of both non dilated and obstructed collecting systems in patients with normal or moderately impaired renal function.

I.V.U can be abandoned as an investigation because of cost, risks associated with contrast media and radiation exposure.

T1 T2

LOW SIGNAL (BLACK) water bone

HIGH SIGNAL (WHITE) BoneFat

water

Normal MRI of the kidneys. The appearance of the kidneys is variable on MR imaging depending on imaging factors. The top left image is a T1-weighted sequence and the top right is T2 weighted. The bottom images were obtained after gadolinium injection and demonstrate the corticomedullary and nephrographic phases.

Normal MR imaging of the kidneys. This image was obtained in the coronal plane and after gadolinium injection

CASE 1

73yo Malay retired farmer with underlying case of hypertension and hyperlipidemia (30yrs) was diagnosed having kidney stone for the past 10yrs. US KUB, X-ray KUB, urinalysis, DTPA was done in 23Aug2006 but defaulted follow-up since then.

Admit again on last 2 month presented with fever and lower urinary tract symptoms (urosepsis). CT-scan was done.

Currently admitted for left renal nephrectomy.

Results of imaging: US KUB

3.5 x 1.6cm DTPA (23/8/06) - Diethylenetriamene pentaacetate

Left staghorn calculi with thin cortex & atrophic kidney. Slightly small size of right kidney with adequate function. No subrenal obstruction. Grossly reduced left kidney with adequate negligible

function ( EGFR 47.85 ml/min). CT-scan (18/8/11)

Imp: small left kidney with partial left staghorn calculi.

The right kidney is smooth in outline measuring 9.1cm in bipolar length.

Multiple small renal parenchymal cysts with the largest in the medial lower pole (exophytic) measuring 1.0cm in diameter.

No renal calculus, parenchymal calcification nor hydronephrosis.

The left kidney is irregular in outline and relatively small in size (6.5cm in bipolar length) with thin parenchyma especially at the lower pole.

An exophytic renal parenchymal cyst measuring 1.0cm in diameter noted at the upper pole.

Staghorn calculus noted occupying the renal pelvis and the lower pole calyces, the largest diameter in the pelvis is 1.5cm x 1.0cm x 2.9cm in size.

Multiple small scattered parenchymal calcifications in the midpole and upper pole with the largest in the midpole measuring 0.5cm in size.

Both ureters are not dilated. No hydronephrosis bilaterally. Urinary bladder is underfilled. Scattered aortic wall and illiac arteries calcification. Degenerative changes of the visualised spine. Impression: Small left kidney with partial staghorn calculus

REFERENCE

Urinary Tract Calculi webpage. Located at http://www.cewebsource.com/coursePDFs/CTurinaryTract.pdf. Expires May 15, 2013.

Medina, L. Santiago.; Blackmore, Christopher Craig. Evidence-based Imaging: Optimizing Imaging in Patient Care.

Case from 2I and 7S.

Issues of Imaging of Nephrolithiasis I. What is the appropriate test for suspicion of obstructing

ureteral stone? II. How should stones be followed after treatment? III. Special case: the pregnant patient