1 Department of Gastrointestinal and Hepato-Biliary-Pancreatic Surgery, Nippon Medical School, 113-8602, 1-1-5 Sendagi, Bunkyo-ku, Tokyo, Japan. Electronic address: takumaiwai@nms.ac.jp.
2 Department of Gastrointestinal and Hepato-Biliary-Pancreatic Surgery, Nippon Medical School, 113-8602, 1-1-5 Sendagi, Bunkyo-ku, Tokyo, Japan. Electronic address: s-shinji@nms.ac.jp.
3 Department of Gastrointestinal and Hepato-Biliary-Pancreatic Surgery, Nippon Medical School, 113-8602, 1-1-5 Sendagi, Bunkyo-ku, Tokyo, Japan. Electronic address: y-tak@nms.ac.jp.
4 Department of Gastrointestinal and Hepato-Biliary-Pancreatic Surgery, Nippon Medical School, 113-8602, 1-1-5 Sendagi, Bunkyo-ku, Tokyo, Japan. Electronic address: hiroshiy@nms.ac.jp.