Department of Gastroenterological Surgery, Osaka University Graduate School of Medicine, 2-2-E2 Yamada-oka, Suita City, Osaka, 565-0871, Japan. kyamashita@gesurg.med.osaka-u.ac.jp. Department of Gastroenterological Surgery, Osaka University Graduate School of Medicine, 2-2-E2 Yamada-oka, Suita City, Osaka, 565-0871, Japan. Department of Surgery, Osaka General Medical Center, Osaka, Japan. Department of Surgery, Kindai University Faculty of Medicine, Osaka, Japan.