Shoko Ono1, Satoshi Abiko2, Mototsugu Kato3. 1. Division of Endoscopy, Hokkaido University Hospital, Sapporo, Japan. 2. Department of Gastroenterology, Hokkaido University Graduate School of Medicine, Japan. 3. Department of Gastroenterology, National Hospital Organization Hakodate Hospital, Hakodate, Japan.