1. Department of Gastroenterology and Hepatology, Yokohama City University School of Medicine, Yokohama, Japan
2. Department of Medical Education, Yokohama City University School of Medicine, Yokohama, Japan
3. Department of Gastroenterology, Hiratsuka City Hospital, Hiratsuka, Kanagawa, Japan
4. Department of Pathology, Yokohama City University Graduate School of Medicine, Yokohama, Kanagawa, Japan