Acute flank pain: a modern approach to diagnosis and management.

Acute flank pain is a common and complex clinical problem. In addition to flank pain caused by ureterolithiasis, other urinary and extraurinary abnormalities can result in a similar clinical picture. Unenhanced CT can rapidly, accurately, and safely determine the presence or absence of ureteral obstruction. When obstruction is caused by ureterolithiasis, CT allows precise determination of stone size and location. These are the two most important factors used for patient management. In addition to direct stone visualization, there are many secondary CT signs of ureteral obstruction that are direct manifestations of the underlying pathophysiology. On the other hand, when obstruction is absent, CT can diagnose or exclude most other abnormalities that result in flank pain. As a result of its many advantages, unenhanced helical CT should become the dominant imaging modality for evaluation of all patients with acute flank pain in whom a clinical diagnosis is uncertain.