1. Center for Gastroenterology Teine Keijinkai Hospital, Sapporo, Hokkaido, Japan
2. Department of Gastroenterology and Hepatology, Tokyo Medical University Hospital, Tokyo, Japan
3. Toho University Omori Medical Center, Tokyo, Japan
4. Kyoto Second Red Cross Hospital, Kyoto, Japan
5. Kitasato University Hospital, Kanagawa, Japan