1. Department of Gastroenterology and Hepatology; Tokyo Medical University; 6-7-1 Nishishinjuku, Shinjuku-ku Tokyo 160-0023 Japan
2. Third Department of Surgery; Tokyo Medical University; Tokyo Japan
3. Department of Digestive Surgery; Hachioji Medical Center of Tokyo Medical University; Tokyo Japan
4. Department of Gastroenterology, Graduate School of Medicine; The Tokyo University; Tokyo Japan