Corresponding Author: Yu-Ling Sun, MD, PhD, Institute of Hepatobili- ary and Pancreatic Diseases, Department of Hepatobiliary and Pancreatic Surgery, First Affiliated Hospital, Zhengzhou University, School of Medicine, Zhengzhou 450052, China (Te1:+86-371-66862122; Fax: +86-371-66964927; Email: ylsun@zzu.edu.cn)