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.