1. Department of General and Gastroenterological Surgery, Osaka Medical and Pharmaceutical University, Takatsuki, Japan
2. Department of Healthcare Quality Assessment, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
3. Department of Gastrointestinal Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
4. Department of Surgery, Japan Baptist Hospital, Kyoto, Japan
5. Department of Gastroenterological and Pediatric Surgery, Gifu University School of Medicine, Gifu, Japan
6. Department of Surgery, Kochi Medical School, Nankoku, Japan
7. Tokai Central Hospital, Kakamigahara, Japan
8. Database Committee, The Japanese Society of Gastroenterological Surgery, Tokyo, Japan
9. The Japanese Society of Gastroenterological Surgery, Tokyo, Japan