Chao Dong1, Shi Chang2, Huihuan Tang3. 1. Department of General Surgery, Xiangya Hospital, Central South University, Changsha, China; Xiangya International Medical Center, Xiangya Hospital, Central South University, Changsha, China. 2. Department of General Surgery, Xiangya Hospital, Central South University, Changsha, China 410008. 3. Department of General Surgery, Xiangya Hospital, Central South University, Changsha, China 410008. Electronic address: huihuan.tang@hotmail.com.