An abnormality involving the genitourinary tract is detected in 1 in 50 to 1 in 100 pregnancies, depending on the sonographic criteria. The goal of management is to recognize and treat congenital anomalies that may adversely affect renal function or cause urinary tract infection (UTI) or sepsis. Many structural abnormalities of the urinary tract are characterized by hydronephrosis, which frequently is assumed to be obstructive. However, often antenatal hydronephrosis (ANH) results from non-obstructive causes, including vesicoureteral reflux (VUR), multicystic dysplastic kidney, and certain abnormalities of the ureteropelvic and ureterovesical junction.