1. From the Departments of Radiology (K.G.S., R.K.V., A.A.A.B., M.Z., M.U.A., M.L.R.) and Nephrology (A.A.A.B.), University of Alabama at Birmingham, 619 19th St S, Birmingham, AL 35233; and Department of Radiology, Mayo Clinic, Jacksonville, Fla (L.F.A., D.M.S., M.P.C., M.J.C.).