1. The Institute for Adult Diseases, Asahi Life Foundation, 1-9-14 Nishi-Shinjuku, Shinjuku-ku, Tokyo 160-0023,1 and
2. Division of Gastroenterology, Department of Internal Medicine, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655,2 Japan