1. Department of Gastroenterology and Hepatology, Hakodate Municipal Hospital, Hakodate, Japan
2. Department of Gastroenterology and Hepatology, Hokkaido University Faculty of Medicine and Graduate School of Medicine, Sapporo, Japan
3. Department of Endoscopy, The Jikei University School of Medicine, Tokyo, Japan
4. Department of Nursing, Hakodate Municipal Hospital, Hakodate, Japan