Yao Cheng1, Qianbin Jia1, Xianze Xiong1, Nansheng Cheng2. 1. Department of Bile Duct Surgery, West China Hospital, Sichuan University, Chengdu, China. 2. Department of Bile Duct Surgery, West China Hospital, Sichuan University, Chengdu, China. Electronic address: nanshengcheng@gmail.com.