Sensitivity of gray scale ultrasound in detecting urinary tract obstruction.

To determine the reliability of gray scale ultrasound in detecting urinary tract obstruction, a prospective study of 67 patients examined by both excretory urography and ultrasound was undertaken. The degree of hydronephrosis was defined by urographic criteria, and the corresponding echograms were analyzed without knowledge of the urographic results. Hydronephrosis was correctly diagnosed by ultrasound in 46 of 47 kidneys shown to be obstructed on urography, for a sensitivity of 98%. Our results show that when obstruction is the sole clinical question, ultrasound is an effective screening test. Thus many patients with a variety of medical diseases of the kidney can be spared excretory urography.