1. Department of General Surgery, Tangdu Hospital, Fourth Military Medical University, Xi'an, 710038, China
2. Department of General Surgery, 943 Hospital of PLA, Wuwei, 733000, China
3. School of Clinical Medicine, Xi'an Medical University, Xi'an, 710032, China
4. Department of Military Preventive Medicine, Fourth Military Medical University, Xi'an, 710032, China