Clinical characteristics of ureteral calculi detected by nonenhanced computerized tomography after unclear results of plain radiography and ultrasonography

PURPOSE: Prospective non-enhanced computerized tomography (CT) was performed for patients presenting with renal colic and showing negative or equivocal results on plain x-ray of the kidneys, ureters and bladder (KUB) as well as ultrasonography (US) to evaluate the usefulness of plain CT. We also evaluated the clinical characteristics of urinary calculi detected under such conditions. MATERIALS AND METHODS: Between January 2000 and June 2002, 560 patients presented with acute unilateral renal colic. Of these patients 238 negative or equivocal for ureteral calculus on KUB and US underwent non-enhanced CT. The diagnostic value of plain CT in patients with negative or equivocal KUB and US was determined, and results and other clinical findings were compared. Clinical characteristics of ureteral stones detected by plain CT were compared with those of stones diagnosed by KUB and US. RESULTS: By plain CT 143 (60.1%) and 6 (2.5%) cases of pain were determined to have been caused by ureteral stones and other pathogeneses, respectively. No definitive diagnosis was obtained in 89 (37.4%). Stone size detected by plain CT was significantly smaller than controls (3.77 vs 6.37 mm, p <0.0001) and tended to be located in the middle or lower ureter (76.2% or 109 of 143 vs 52.2% or 168 of 322, p <0.0001). Symptoms spontaneously improved in 137 (95.8%) after conservative therapy while 6 underwent intervention, a rate significantly lower (p <0.0001) than controls (32.9% or 106 of 322). CONCLUSIONS: Non-enhanced CT is a useful modality for diagnosis of patients presenting with acute renal colic but whose results are negative or equivocal on KUB and US. Excretory urography is rarely needed because stones undetected on KUB and US tend to be small and in the middle or lower ureter, and spontaneous passage is expected.