1. Department of Gastroenterology, The Shanghai Tenth People's Hospital of Tongji University, Shanghai 200072, P.R. China
2. Department of General Surgery, Zhongshan Hospital of Fudan University, Shanghai 200032, P.R. China
3. Department of Gastroenterology, Zhengzhou Central Hospital Affiliated to Zhengzhou University, Zhengzhou, Henan 450007, P.R. China