1. Department of General Internal Medicine Saitama Medical University Saitama Japan
2. Center for Diagnostic and Therapeutic Endoscopy, School of Medicine Keio University Tokyo Japan
3. Department of Gastroenterology Kyorin University Hospital Tokyo Japan
4. Department of Gastroenterology Saitama Medical University Saitama Japan
5. Division of Gastroenterology and Hepatology, Department of Internal Medicine Keio University School of Medicine Tokyo Japan