Prognostic value of initial renal ultrasound in patients with posterior urethral valves

Increased cortical echogenicity and loss of corticomedullary differentiation on the initial renal ultrasound study are said to be predictive of poor renal function in patients with posterior urethral valves. We reviewed ultrasound results in a group of patients with posterior urethral valves to test this hypothesis.

We reviewed the radiology records of 19 patients in year 1 of life with posterior urethral valves seen since 1976 for whom records were available. The degree of corticomedullary differentiation and cortical echogenicity was compared with serum creatinine after 4 days of catheter drainage and creatinine clearance at the most recent followup.

Median followup was 96 months. At the last followup the sensitivity, specificity, and positive and negative predictive values of increased cortical echogenicity and loss of corticomedullary differentiation for predicting creatinine clearance less than 69 ml. per minute per 1.73 m.2 were 90, 57, 75 and 80, and 100, 33, 71 and 100%, respectively.

Increased cortical echogenicity and loss of corticomedullary differentiation are relatively insensitive predictors of eventual renal function in boys with posterior urethral valves. In a significant proportion of patients with normal renal function the initial renal ultrasound study revealed echogenic kidneys, although only a small proportion with poor renal function had normal kidneys.