1. Department of General Surgery, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shanxi 710061, P.R. China
2. Department of Geriatrics, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, P.R. China
3. Department of General Surgery (Gastrointestinal Surgery), The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, P.R. China