1. Department of Surgery, Furano Kyokai Hospital , Furano, Hokkaido 076-8765, Japan
2. Department of Surgery, Asahikawa Kosei Hospital , Asahikawa, Hokkaido 078-8211, Japan
3. Department of Hepatobiliary , Pancreatic and Transplant Surgery, , Asahikawa, Hokkaido 078-8510, Japan
4. Asahikawa Medical University , Pancreatic and Transplant Surgery, , Asahikawa, Hokkaido 078-8510, Japan
5. Department of Digestive Surgery, Asahikawa Medical University , Asahikawa, Hokkaido 078-8510, Japan