1. Graduate School of Medicine, Department of Gastroenterology, The University of Tokyo, Bunkyo-ku, Japan
2. First Department of Internal Medicine, Gifu University Hospital, Gifu, Japan
3. Faculty of Medicine, Department of Gastroenterology and Hepatology, Kindai University, Osaka, Japan
4. Department of Gastroenterology, Juntendo University School of Medicine, Graduate School of Medicine, Bunkyo-ku, Japan