The postnatal management of the antenatally detected ureteropelvic junction obstruction relies on several factors, including the degree of hydronephrosis detected postnatally, the renogram washout curve, and the degree of renal function. It is imperative for the urologist to review all renal scans because of the inherent pitfalls in performing and interpreting these studies. A select population demonstrating severe pyelocaliectasis and poor function exists in which an intraoperative renal biopsy may be a better predictor of future renal function when compared with the preoperative renal scan. We present a patient with poor renal function that normalized with early surgical intervention.