1. Second Department of Surgery Dokkyo Medical University Tochigi Japan
2. Department of Healthcare Quality Assessment The University of Tokyo 880 Kitakobayashi, Mibu Tochigi321-0293Japan
3. Department of Health Policy and Management School of Medicine Keio University Tokyo Japan
4. The Japanese Society of Gastroenterological Surgery Tokyo Japan
5. Database Committee The Japanese Society of Gastroenterological Surgery Tokyo Japan
6. The Japanese Society of Hepato‐Biliary‐Pancreatic Surgery Tokyo Japan