F Bian1, G L Zhang2, F M Wang3, D Yang4, Y Y Gao3, J Li3, Y Li3. 1. Drpartment of Gastroenterology, Beilun District People's Hospital in Ningbo City, Ningbo 315800, China. 2. Department of Gastroenterology , The First Central Hospital of Tianjin, Tianjin 300192, China. 3. Department of Gastroenterology and Hepatology, The Third Central Hospital of Tianjin, Tianjin 300170, China. 4. Department of Gastroenterology, The First Central Clinical College, Tianjin Medical University, Tianjin 300070, China.