1. Department of General Surgery, Kyouwa Chuo Hospital, Chikusei-shi, Ibaraki, Japan
2. Department of Gastroenterological Surgery, Dokkyo Medical University, Mibumachi, Shimotsuga-gun, Tochigi, Japan
3. Department of Surgery, the Mutual Aid Association for Teachers and Officials Sanraku Hospital, Chiyoda-ku, Tokyo, Japan