Antenatal hydronephrosis: differential diagnosis, evaluation, and treatment options

The diagnosis, evaluation and management of antenatal hydronephrosis has undergone a two stage paradigm shift since the advent of prenatal ultrasonography in the early 1980s. Initially the identification of a large number of asymptomatic infants appeared to afford the surgeon the opportunity for preemptive intervention. However, it has now become apparent that antenatal hydronephrosis (AH) is far more difficult to interpret than originally perceived. The initial enthusiasm for surgery has now been replaced by a much more conservative approach to ureteropelvic junction(UPJ) obstruction, multi-cystic dysplastic kidney(MCDK), vesicoureteral reflux and the non-refluxing megaureter. This review will highlight the postnatal evaluation of AH and include an overview of the Society for Fetal Urology grading system for hydronephrosis. The differential diagnosis and treatment options for UPJ obstruction, vesicoureteral reflux, MCDK, duplication anomalies, megaureter, and posterior urethral valves will be discussed.