1. Department of General Surgery, Mianyang Central Hospital, Mianyang Central Hospital of Chongqing Medical University, Mianyang 621000, Sichuan Province, P.R. China
2. Department of Gastroenterological Surgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing Medical University, Yuzhong 400016, Chongqing, P.R. China