Unenhanced helical computed tomography in the evaluation of acute flank pain

Objectives: The purpose of this study was to determine the value of unenhanced helical computed tomography (UHCT) in the diagnosis of acute flank pain at our institution. Methods: Two hundred and thirty-three consecutive UHCT examinations, performed for suspected renal/ureteral colic between July 2000 and August 2001 were reviewed, along with pertinent medical records. Results: Ureteral calculi were identified in 148 (64%) examinations, evidence of recent passage of calculi was found in 10 (4%) and no calculi were found in 75 (32%). Thirty-two of the conservatively managed patients were excluded for inadequate follow-up. In the remaining 201 patients, sensitivity of UHCT in diagnosing calculi was 99% and specificity was 98%, while the positive predictive value was 99% and negative positive predictive value was 98%. Overall, an alternative or additional diagnosis was established in 28 (12%) patients. Upon diagnosis of ureterolithiasis on UHCT, none of the patients required additional imaging studies for confirmation. Conclusion: UHCT is a highly sensitive imaging modality for the detection of urinary tract calculi and obstruction.