1. Department of Hepatobiliary Surgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400060, P.R. China
2. Department of Gastroenterology, The Fifth People's Hospital of Chongqing, Chongqing Hospital of Integrated Traditional Chinese and Western Medicine, Chongqing 400060, P.R. China
3. Department of Anesthesiology, Nan'an District People's Hospital of Chongqing, Chongqing 400060, P.R. China
4. Department of General Surgery, Nan'an District People's Hospital of Chongqing, Chongqing 400060, P.R. China