1. Department of Surgery; Gastroenterological Surgery; Graduate School of Medicine; Osaka University; Osaka Japan
2. Department of Healthcare Quality Assessment; Graduate School of Medicine; The University of Tokyo; Tokyo Japan
3. Department of Regenerative Surgery; Fukushima Medical University; Fukushima Japan
4. Second Department of Surgery; Hamamatsu University School of Medicine; Hamamatsu Japan
5. Database Committee; The Japanese Society of Gastroenterological Surgery; Tokyo Japan
6. The Japanese Society of Gastroenterological Surgery; Tokyo Japan