1. Department of Gastroenterology and Hepatology, Zhongshan Hospital, Fudan University, Shanghai, P. R. China
2. Division of Gastroenterology, Hepatology and Nutrition, Department of Medicine, University of Florida, Gainesville, Florida, United States
3. Endoscopy Center and Endoscopy Research Institute, Zhongshan Hospital, Fudan University, Shanghai, P. R. China