1. Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, 2-1 Midorigaoka-higashi, Asahikawa, Hokkaido 078-8510, Japan
2. Division of Gastroenterological and General Surgery, Department of Surgery, Asahikawa Medical University, 2-1 Midorigaoka-higashi, Asahikawa, Hokkaido 078-8510, Japan
3. Department of Gastroenterology, Sapporo Higashi Tokushukai Hospital, 3-1 North 33-jou East 14-chome East Ward, Sapporo, Hokkaido 065-0033, Japan