1. Musashino Red Cross Hospital, Tokyo, Japan;
2. The University of Tokyo, Tokyo, Japan;
3. Nihon University School of Medicine, Department of Digestive Surgery, Tokyo, Japan;
4. Department of Surgery, Meiwa Hospital, Nishinomiya, Japan;
5. Kindai University, Faculty of Medicine, Osaka, Japan;
6. Tokushima University, Tokushima, Japan;
7. Oita University, Oita, Japan;
8. Kanazawa University Hospital, Kanazawa, Japan;
9. Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan;
10. 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, University of Tokyo, Tokyo, Japan;
14. National Center for Global Health and Medicine, Tokyo, Japan;