1. Department of Hepato–Biliary–Pancreatic and Transplant Surgery Fukushima Medical University Fukushima Japan
2. Endowed Course for Health System Innovation Keio University School of Medicine Tokyo Japan
3. Department of Healthcare Quality Assessment, Graduate School of Medicine The University of Tokyo Tokyo Japan
4. Database Committee The Japanese Society of Gastroenterological Surgery Tokyo Japan
5. Department of Health Policy and Management Keio University School of Medicine Tokyo Japan
6. The Japanese Society of Gastroenterological Surgery Tokyo Japan