1. Department of Gastrointestinal Surgery, Xijing Hospital of Digestive Diseases, The Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
2. Department of Emergency, Xijing Hospital, The Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
3. Department of General Surgery, Xi'an Central Hospital, Xi'an, Shaanxi 710003, P.R. China