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.

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. Once identified, the patient's grade of hydronephrosis will be recorded from initial ultrasound based on Society of Fetal Urology (SFU) classification. If no initial SFU classification was assigned to the hydronephrosis a pediatric radiologist will review the initial ultrasound images and classify the grade of hydronephrosis based upon SFU criteria. The patients ensuing evaluation of their hydronephrosis that took place will then be recorded and de-identified. Data to be collected will include: Ultrasound evaluations of the abdomen, retroperitoneum, or renal system, Voiding Cysto-Urethrogram (VCUGs), nuclear studies: diuretic enhanced technetium-99m dietylene triamine penta-acetic acid renogram (DTPA) or technetium-99m Mercapto-acetyl-triglycine renogram (MAG3), referral to pediatric urology for pyeloplasty, serum electrolytes, Blood Urea Nitrogen (BUN) and creatinine, urinalysis, urinary tract infections, and placement on long-term antibiotic prophylaxis.

The follow up evaluation that took place for each patient will then be compared to our proposed algorithm for congenital hydronephrosis evaluation and treatment. This algorithm will be designed based on clinical experience of expert opinion and literature review of each step in the evaluation and treatment. Primary outcomes will be progressive renal function decline and progression to referral to a pediatric urologist for pyeloplasty. Secondary outcomes will be incidence of urinary tract infections and placement on long term antibiotic prophylaxis for urinary tract infection prophylaxis.

Inclusion Criteria:

• Inclusion criteria for the study were confirmation of the diagnosis of prenatal hydronephrosis by postnatal renal ultrasound

Exclusion Criteria:

• prior history of UTI
• diagnosis of cystic renal dysplasia with poorly functioning kidney
• previous operation on the urinary tract system
• and other deformities of the external genital organs or anomalies in cardiopulmonary and central nervous system

Infants with prenatally diagnosed hydronephrosis by ultrasound who have consulted pediatric nephrology