1. Department of Gastroenterology and Hepatology, Hokkaido University Hospital, Kita 15, Nishi 7, Kita-ku, Sapporo, Hokkaido 060-8638, Japan
2. Department of Gastroenterology and Hepatology, Hokkaido University Hospital, Sapporo, Hokkaido, Japan
3. Division of Cancer Center, Hokkaido University Hospital, Sapporo, Hokkaido, Japan