Is there a learning curve in diagnosing urolithiasis with noncontrast helical computed tomography?

Objective: To report one department's experience with helical computed tomo graphic (HCT) evaluation of patients with suspected renal colic to diagnose ureteral calculi; to determine whether there is a learning curve in perfor ming HCT in this context; and to determine whether HCT for the evaluation o f renal colic exposes patients to more radiation than the standard intraven ous pyelography (IVP) combined with nephrotomography. Methods: All patients presenting to the emergency department with flank or abdominal pain were e valuated with nonreformatted noncontrast HCT. To determine changes in diagn ostic accuracy, patients were divided into 2 groups: those evaluated betwee n September 1996 and January 1997 (group 1, 67 patients), and those seen fr om February to June 1997 (group 2, 53 patients). A radiation exposure study was performed using phantoms, and radiation exposure for HCT, IVP and neph rotomography was measured. Results: Review of HCT scans to diagnose uretera l calculi had a sensitivity of 91.7%, specificity of 82.6%, and accuracy of 87.2% in group 1, and a sensitivity of 95.5%, specificity of 86.7%, and ac curacy of 91.9% in group 2. Patients undergoing IVP with nephrotomography w ere exposed to an effective dose equivalent of 343 mrem (dSv) (for men) and 664 mrem (for women). The effective dose equivalent for an HCT scan was 18 0 mrem. Conclusion: HCT offers excellent, rapid diagnostic accuracy without the need for intravenous contrast medium and with a lower radiation exposu re level than IVP in evaluating patients with acute flank pain. There is a small but real learning curve in evaluating patients with acute flank pain with HCT.