1. Department of Gastroenterology Kitasato University of Medicine Sagamihara Kanagawa Japan
2. Department of Gastroenterology International University of Health and Welfare Ichikawa Hospital Ichikawa‐shi Chiba Japan
3. Department of Pathology Yuri Kumiai General Hospital Yurihonjo Akita Japan
4. Division of Gastroenterology and Hepatology, Department of Medicine Nihon University School of Medicine Tokyo Japan