Patients will be followed for 7 days after surgery or until the day of hospital discharge, whichever occurs first. Data collected from the hospital chart will include: demographics, medical and surgical history, type of surgical procedure, underlying congenital heart disease, baseline serum creatinine and renal function, serum creatinine(s) throughout hospitalization, daily urine output, need for dialysis, date of death or discharge. The primary endpoint is development of AKI based on serum creatinine reaching double baseline or requirement for acute dialysis, as described in the RIFLE- Risk, Injury, Failure, Loss, and End Stage Renal Disease- model of renal insufficiency.