[1] Keio Univ, Sch Med, Dept Surg, 35 Shinanomachi,Shinjuku Ku, Tokyo 1608582, Japan
[2] Univ Tokyo, Grad Sch Med, Dept Healthcare Qual Assessment, Tokyo, Japan
[3] Japanese Soc Gastroenterol Surg, Project Management Subcomm, Tokyo, Japan
[4] Japanese Soc Gastroenterol Surg, Database Comm, Tokyo, Japan
[5] Natl Def Med Coll, Dept Surg, Saitama, Japan
[6] Univ Tokyo, Grad Sch Med, Dept Gastrointestinal Surg, Tokyo, Japan
[7] Japan Esophageal Soc, Tokyo, Japan
[8] Japanese Soc Gastroenterol Surg, Tokyo, Japan