1. The Japanese Society of Gastroenterological Surgery Database Committee Tokyo Japan
2. Hamamatsu University School of Medicine Hamamatsu Japan
3. Second Department of Surgery Hamamatsu University School of Medicine Hamamatsu Japan
4. Department of Health Policy and Management School of Medicine Keio University Tokyo Japan
5. Department of Healthcare Quality Assessment Graduate School of Medicine The University of Tokyo Tokyo Japan
6. The Japanese Society of Gastroenterological Surgery Tokyo Japan