1. Department I of Gastrointestinal Surgery, Weihai Central Hospital, Weihai, Shandong 264400, P.R. China
2. Department Ⅲ of Oncology, Weihai Central Hospital, Weihai, Shandong 264400, P.R. China
3. Department Ⅱ of Gastrointestinal Surgery, Weihai Central Hospital, Weihai, Shandong 264400, P.R. China