1. Department of Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing 100020, P.R.�China
2. Department of Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing 100020, P.R. China
3. Department of Gastroenterology, Beijing Friendship Hospital, Capital Medical University, Beijing Key Laboratory for Precancerous Lesion of Digestive Diseases, National Clinical Research Center for Digestive Diseases, Beijing 100050, P.R.�China