1. Department of Gastroenterology, the Sixth Affiliated Hospital, Sun Yat-sen University , Guangzhou, P. R. China
2. Guangdong Provincial Key Laboratory of Colorectal and Pelvic Floor Diseases, the Sixth Affiliated Hospital, Sun Yat-sen University , Guangzhou, P. R. China
3. Department of Small Bowel Endoscopy, the Sixth Affiliated Hospital, Sun Yat-sen University , Guangzhou, P. R. China
4. Center for Inflammatory Bowel Diseases, Columbia University Irving Medical Center-New York Presbyterian Hospital , New York, USA