1. Division of Gastroenterological, Hepato-Biliary-Pancreatic, Transplantation and Pediatric Surgery, Department of Surgery, Shinshu University School of Medicine, Asahi, Matsumoto, Japan.
2. The Database Center of the National University Hospitals, The University of Tokyo Hospital, Tokyo, Japan.
3. Division of Medical Information Technology and Administration Planning, Kyoto University Hospital, Kyoto, Japan.