Unenhanced helical computed tomography in the evaluation of acute flank pain.

Noncontrast helical computed tomography has rapidly replaced other imaging modalities in the evaluation of patients with acute flank pain. New studies from multiple centers have compared helical computed tomography directly with intravenous urography in large numbers of patients, confirming the value of the former. It is highly sensitive and specific for the diagnosis of ureterolithiasis, including the visualization of ureteral calculi and secondary signs of obstruction. It can evaluate alternate diagnoses, improving the utility of noncontrast helical computed tomography as a diagnostic tool in the evaluation of acute flank pain.