1. Division of Gastroenterology and Hepatology, Department of Internal Medicine, St. Marianna University School of Medicine, Kawasaki, Japan
2. Department of Internal Medicine, Kawasaki Rinko General Hospital, Kawasaki, Japan
3. Department of Gastroenterology and Hepatology, Hokkaido University Graduate School of Medicine, Sapporo, Japan
4. Division of Endoscopy, Hokkaido University Hospital, Sapporo, Japan
5. Department of Gastroenterology, National Hospital Organization Hakodate Hospital, Hakodate, Japan