Patients with congenital hydronephrosis will be identified by inpatient consultations performed by Dr. Assadi for congenital hydronephrosis and by outpatient problem lists with congenital hydronephrosis of Dr. Assadi's existing patients. Given standard evaluation will be evaluated to determine if based on initial ultrasound classification an algorithm can be developed to target evaluation studies for the initial evaluation. With a goal of targeting the few children that have need of additional intervention and minimizing the studies performed on children who will spontaneously resolve.