1. Department of Surgery, Gastroenterological Center, Yokohama City University Medical Center, Minami-ku, Yokohama, Japan
2. Department of Surgery, Surgical Oncology and Science, Sapporo Medical University, Chuo-ku, Sapporo, Japan
3. Department of Surgery, Kouseiren Takaoka Hospital, Takaoka, Toyama, Japan
4. Department of Gastroenterological Surgery, Toyonaka Municipal Hospital, Toyonaka, Osaka, Japan
5. Department of Lower Gastroenterological Surgery, Hyogo College of Medicine, Nishinomiya, Japan
6. Department of Surgery, Yokosuka Kyosai Hospital, Nakahara-ku, Kawasaki, Kanagawa, Japan
7. Department of Surgery, Osaka Rosai Hospital, Sakai, Osaka, Japan
8. Department of Surgery, Southern TOHOKU Research Institute for Neuroscience, Southern TOHOKU General Hospital, Yatsuyamada, Koriyama, Japan
9. Department of Gastroenterological Surgery, Ikeda City Hospital, Ikeda, Osaka, Japan
10. Department of Gastroenterological Surgery, Toranomon Hospital, Minato City, Tokyo, Japan
11. Department of Surgery, Fujisawa City Hospital, Fujisawa, Kanagawa, Japan
12. Department of Gastroenterological Surgery, Osaka International Cancer Institute, Chuo-ku, Osaka, Japan
13. Department of Surgery, National Hospital Organization Osaka National Hospital, Chuo Ward, Osaka, Japan
14. Department of Gastroenterological Surgery, Yokohama City University Graduate School of Medicine, Yokohama, Japan
15. Department of Surgery, Kanagawa Cancer Center, Yokohama, Kanagawa, Japan
16. Department of Surgery, Kitasato University Kitasato Institute Hospital, Minato City, Tokyo, Japan
17. Department of Surgery, Yokohama Municipal Citizen’s Hospital, Yokohama, Kanagawa, Japan
18. Division of Surgery Gastroenterological Center, Medico Shunju Shiroyama Hospital, Osaka, Japan
19. Division of Surgery, Gastrointestinal Center, Yokohama Shin-Midori General Hospital, Yokohama, Japan
20. Department of Biostatistics, Yokohama City University School of Medicine, Yokohama, Japan