1. Kindai University Faculty of Medicine, Osaka, Japan;
2. Hepato-Biliary-Pancreatic Surgery Division, Department of Surgery, Gradiate School of Medicine,The University of Tokyo, Tokyo, Japan;
3. Department of Digestive Surgery, Nihon University School of Medicine, Tokyo, Japan;
4. Department of Gastroenterology and Hepatology, Musashino Red Cross Hospital, Tokyo, Japan;
5. Department of Surgery, Meiwa Hospital, Nishinomiya, Japan;
6. Tokushima University, Tokushima, Japan;
7. Oita University, Oita, Japan;
8. Department of Gastroenterology, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, Japan;
9. Department of Gastroenterological Surgery, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan;
10. The University of Tokyo, Tokyo, Japan;
11. Yamanashi Prefectural Central Hospital, Kofu, Japan;
12. Towa Hospital, Tokyo, Japan;
13. Department of Biostatistics, School of Public Health, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan;
14. National Center for Global Health and Medicine, Tokyo, Japan;