1. Department of General and Colorectal Surgery, Beijing Shijitan Hospital, Capital Medical University, Beijing, China
2. Department of Gastroenterology & Hepatology, Chinese PLA General Hospital, Beijing, China
3. Beijing Municipal Key Laboratory of Clinical Epidemiology, School of Public Health, Capital Medical University, Beijing, China
4. Department of General and Colorectal Surgery, Beijing Shijitan Hospital, The Ninth Teaching Hospital of Peking University Health Science Center, Beijing, China
5. Department of Surgery, College of Medicine, University of Saskatchewan, Saskatoon, Canada