Can noncontrast helical computed tomography replace intravenous urography for evaluation of patients with acute urinary tract colic?

The objective of this study was to determine whether helical computed tomography (CT) performed without oral or intravenous contrast agents is accurate in the evaluation of patients with suspected acute renal colic. One hundred consecutive patients with suspected renal colic or ureteral colic were referred by our institution's emergency department for unenhanced helical CT scans. We reviewed the original radiographic report for each patient and recorded the size and location of ureteral calculi and other concurrent urinary tract calculi, if any. We also recorded the presence or absence of hydronephrosis, hydroureter, perinephric edema, and periureteral edema. A total of 49 patients had ureteral calculi, 17 patients had only renal calculi, and 34 patients had no stones. Forty-nine patients had ureteral calculi, and 40 (82%) of these 49 patients had associated CT signs including hydroureter and periureteral edema. Calculi were present in the proximal ureter in 11 patients, the midureter in seven patients, and the distal ureter including ureterovesical junction in 31 patients. Calculi were seen elsewhere in the urinary tract and renal pelvis in 44 patients. Other diagnostic tests and stone passage were used to confirm the CT diagnosis of ureteral stones. The sensitivity and specificity of helical CT in evaluating ureteral calculi were 100% and 94%, respectively. Sixteen extraurinary lesions were detected in 34 patients who had no urinary calculi. Most extraurinary lesions (81%) were deemed the cause of acute flank pain. The room time for CT averaged 26 min, compared to 69 min for intravenous urography (IVU). The charge for CT was $600 compared to $400 for IVU in our institution. Unenhanced helical CT was fast and accurate in determining the cause of colic and proved to be highly accurate for emergency situations.