1. Kamishirane Hospital, 2-65-1 Kamishirane, Asahi-ku, Yokohama 241-0002, Japan
2. Department of Surgery, Yokohama City University, 3-9 Fukuura, Kanazawa-ku, Yokohama 236-0004, Japan
3. Department of Gastroenterology, Yokohama City University, Yokohama 236-0004, Japan