Evaluation of azotemic patients: diagnostic yield of initial US examination.

To determine whether renal ultrasound (US) is necessary in all patients with azotemia, the authors retrospectively evaluated renal US examinations in 394 azotemic patients. The patients included 119 patients considered clinically to be at high risk for postrenal urinary obstruction and 275 patients considered to be at low risk. In the high-risk population, 35 patients were found to have hydronephrosis (29%). In the low-risk population, three patients were found to have hydronephrosis (1%). In two of these patients surgical intervention resulted in reversal of the azotemia. The authors recommend that renal US be performed in all high-risk patients and in low-risk patients only if temporization and standard medical treatment do not resolve the azotemia.