Accuracy of renal-bladder ultrasonography as a screening method to suggest posterior urethral valves.

PURPOSE: We determine the usefulness of ultrasonography as a screening modality to support the diagnosis of posterior urethral valves.

MATERIALS AND METHODS: A retrospective chart analysis was performed of 93 consecutive boys with newly diagnosed posterior urethral valves from August 1985 through February 1999. Of the 93 boys 65, including 62 who underwent renal and bladder ultrasonography, had preoperative renal sonography available and constitute our study population. Patient age range at presentation was newborn to 13 years, with 33 of the 65 boys presenting as infants (age 1 year or younger). Presentation included fetal hydronephrosis in 13 cases, urinary tract infection in 18, voiding dysfunction in 9, abdominal mass in 6, renal insufficiency in 5, failure to thrive in 4, hematuria in 1 and other in 9.

RESULTS: Preoperative sonography identified bilateral hydronephrosis in 48 boys (74%), unilateral hydronephrosis in 9 (14%) and no hydronephrosis in 8 (12%). Bladder sonography revealed an abnormal bladder (thickened, trabeculated and/or significantly distended) in 54 boys (87%). An abnormal bladder was seen in 43 of the 46 boys with bilateral hydronephrosis, 6 of 8 boys with unilateral hydronephrosis and 5 of 8 with normal upper tracts. Only 3 of the 62 boys (5%) had a normal upper tract and bladder. The sensitivity of renal ultrasonography in suspecting posterior urethral valves was 88%, while sensitivity of renal-bladder ultrasonography was 95%. When stratifying for age younger than 4 years and 4 or older, the sensitivity of predicting posterior urethral valves with renal-bladder ultrasonography was 87% and 98%, respectively.

CONCLUSIONS: While voiding cystourethrography remains the imaging gold standard for the diagnosis of posterior urethral valves, renal-bladder ultrasonography is an appropriate screening study for a boy suspected to have the condition. Renal-bladder ultrasonography may prove particularly useful in the evaluation of the boy with significant voiding dysfunction before deciding on a more invasive study, such as voiding cystourethrography.