1. From the Departments of Radiology (M.A.B., A.M.W., J.C.E., J.S.M.) and Pediatrics, Division of Nephrology (M.P.), Perelman School of Medicine at the University of Pennsylvania, Children’s Hospital of Philadelphia, 34th and Civic Center Blvd, Philadelphia, PA 19104; and Hospital Neonatal Intensive Care Unit, Pediatric Medical Group, Huntington Memorial Hospital, Pasadena, Calif (E.L.R.).