Ultrasound versus excretory urography in evaluating acute flank pain.

To determine the role of ultrasound (US) in patients with acute flank pain and suspected acute urinary tract obstruction, a prospective study was performed on 20 patients comparing US with emergency excretory urography. US was not as sensitive as excretory urography for diagnosing hydronephrosis, for detecting ureteral or renal calcification, or for diagnosing forniceal rupture. Although US is an effective screening modality for hydronephrosis in patients with chronic renal obstruction, it is not useful for evaluating patients with acute flank pain in whom acute obstruction may be present. In this group of patients, excretory urography remains the examination of choice.