1. Department of Internal Medicine, Hakodate Municipal Hospital 1–10–1, Minato-cho, Hakodate 041–8680, Japan.
2. Gastroenterology, Hakodate Municipal Hospital, Hakodate, Japan
3. Hematology & Oncology, Hokkaido University Graduate School of Medicine, Sapporo, Japan
4. Department of Gastroenterology, Hokkaido University Graduate School of Medicine, Sapporo, Japan