Congenital hydronephrosis is one of the most common anomalies identified on antenatal ultrasound. The underlying etiology of congenital hydronephrosis is multifold, ranging from transient hydronephrosis in utero to clinically significant congenital anomalies of the kidney and urinary tract. While traditional management of hydronephrosis was aimed at relieving symptoms, the advent of routine prenatal ultrasound has led to a shift in the goal of treatment to prevention of renal injury in the asymptomatic patient. However, despite this focus on renal preservation, the diagnostic criteria for identification of children "at risk" for renal damage that can be alleviated by surgical treatment remain a subject of debate. Both antenatal and postnatal imaging studies have been evaluated as indicators for potential reversible renal damage and have been used as potential indicators of the need for surgical intervention. The aim of this review is to discuss the current literature regarding the role of postnatal clinical and radiographic evaluation to identify children who may benefit from early surgical intervention.