In order to attempt to explain the pathogenesis of renal calculi, the investigators videotape and document the location and characteristics of each stone, papillae and calyces. One or more small papillary biopsies are taken for analysis to help determine the point of origin of the kidney stone and histological studies are undertaken to determine tissue differences amongst different types of stone formers. Approximately one month after surgery, metabolic studies are undertaken to further review potential causes of stone formation.