[1] Hokkaido Univ, Grad Sch Med, Dept Gastroenterol, Kita Ku, Sapporo, Hokkaido, Japan
[2] Yamagata Prefectural Cent Hosp, Dept Gastroenterol, Yamagata, Japan
[3] Hokkaido Univ Hosp, Div Endoscopy, Sapporo, Hokkaido 060, Japan
[4] Aichi Med Univ, Sch Med, Dept Publ Hlth, Aichi, Japan
[5] Matsue Red Cross Hosp, Dept Gastroenterol, Matsue, Shimane, Japan
[6] Int Med Ctr Japan, Dept Endoscopy, Tokyo, Japan
[7] Kure Kyosai Hosp, Dept Gastroenterol, Kure, Japan
[8] Kyoto Min I Ren Chuoh Hosp, Dept Gastroenterol, Kyoto, Japan
[9] Ibaraki Cent Hosp, Dept Gastroenterol, Ibaraki, Japan
[10] Jichi Med Univ, Dept Infect & Immun, Shimotsuke, Japan