1 Department of Gastroenterology, Beijing Friendship Hospital, National Key Laboratory of Digestive Health, National Clinical Research Center for Digestive Disease, Beijing Digestive Disease Center, Capital Medical University, Beijing, 100050, P. R. China.
2 Department of Gastroenterology, Beijing Friendship Hospital, National Key Laboratory of Digestive Health, National Clinical Research Center for Digestive Disease, Beijing Digestive Disease Center, Capital Medical University, Beijing, 100050, P. R. China. [email protected].