1. Hepatology and Gastroenterology, Yokohama City University Hospital, Kanagawa, Yokohama 236-0004, Japan
2. Office of Postgraduate Medical Education, Yokohama City University Hospital, 3-9 Fukuura, Kanazawa-ku, Kanagawa, Yokohama 236-0004, Japan
3. Division of Gastroenterology, Nippon Medical School, Tokyo 113-8603, Japan
4. Department of General Medicine, Yokohama City University School of Medicine, Kanagawa, Yokohama 236-0004, Japan
5. Department of Gastroenterology, Yokohama City University Hospital, Kanagawa, Yokohama 236-0004, Japan