[1] Univ Tokyo, Grad Sch Med, Dept Gastroenterol, 7 3 1 Hongo,Bunkyo ku, Tokyo 1138655, Japan
[2] Kameda Med Ctr Makuhari CD 2F, 1 3 Nakase,Mihama ku, Chiba, Chiba 2618501, Japan
[3] Univ Tokyo, Grad Sch Med, Next Generat Endoscop Comp Vis, 7 3 1 Hongo,Bunkyo ku, Tokyo 1138655, Japan
[4] Univ Tokyo, Grad Sch Med, Infect Control & Prevent Serv, 7 3 1 Hongo,Bunkyo ku, Tokyo 1138655, Japan
[5] Univ Tokyo, Ctr Int Prevent Med, Grad Sch Med, 7 3 1 Hongo,Bunkyo ku, Tokyo 1138655, Japan
[6] Univ Tokyo, Ctr Epidemiol & Prevent Med, Grad Sch Med, 7 3 1 Hongo,Bunkyo ku, Tokyo 1138655, Japan
[7] Univ Tokyo, Grad Sch Med, Dept Endoscopy & Endoscop Surg, 7 3 1 Hongo,Bunkyo ku, Tokyo 1138655, Japan