Spiral computerized tomography in the evaluation of acute flank pain: A replacement for excretory urography

Purpose: We determined the value of noncontrast enhanced spiral computerized tomography (CT) in the evaluation of suspected renal colic. Materials and Methods: Thin section (5 mm.) noncontrast enhanced CT was used to evaluate 100 patients presenting to the emergency room with flank pain. The 55 patients with ureteral obstruction were followed at the urology outpatient clinic and by telephone interview, while 45 without ureteral obstruction were followed by telephone interview and chart review. Sensitivity, specificity, and positive and negative predictive values for CT were determined, with passage, retrieval or identification of a stone on a retrograde study considered the gold standard for diagnosis. Results: A total of 89 patients had adequate clinical followup to assess outcome accurately. Of 55 patients with ureteral obstruction on CT 11 underwent endoscopic stone removal, while 44 were treated conservatively with stone passage documented in 39. Of the 45 patients without ureteral stones identified 38 did not pass calculi and CT provided a definite diagnosis in 14. There was 1 false-negative study. The results yielded 98% sensitivity, 100% specificity, and 100% positive and 97% negative predictive values. Conclusions: Noncontrast enhanced spiral CT was accurate and reliable in detecting obstructing ureteral calculi in patients with flank pain.