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.