Diagnosis of Stones
Plain Film

Approximately 90% of urinary tract stones are radio-opaque and therefore should be visualized on plain abdominal film or KUB (Kidney, Ureter, and Bladder radiography). Plain radiography can detect large stones on a single film; however, smaller calculi are often obscured or overlooked when they overlie the ribs, vertebral transverse processes, the sacrum and bowel gas and/or stool.

Bilateral staghorn calculus. Plain abdominal film demonstrates densely opaque, branched calculus in the pelvis and calyces of both kidneys (red arrows).

Advantages of Plain Radiography

1. A single film.
2. Can detect large renal calculi

Disadvantages of Plain Radiography

1. Limited value in accurate diagnosis.
2. Small stones can be obscured or overlooked.
3. Common abdominal calcifications (hepatic, pancreatic, gall bladder, venous or arterial origin and costal cartilage) can mimic the appearance of urinary tract stones.
4. Non radio-opaque stones are not seen on plain x-ray.

The abdominal plain film (KUB; kidneys, ureters, bladder) continues to be one of the important imaging studies for detection of urinary calculi as the majority of the stones (approximately 90% are radio-opaque).

Suggested readings
Mutgi A, Williams JW, Nettleman M: Renal colic. Utility of plain abdominal roentgenogram. Arch Intern Med 1991; 151(8): 1589-1592.

Levine JA, Neitlieh J, Verga M, et al: Ureteral calculi in patients with flank pain: Correlation of plain radiography with unenhanced helical CT. Radiology 1997; 204(1): 27-31.

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