1. Department of Gastroenterology, The Sixth Affiliated Hospital, Sun Yat-sen University , Guangzhou, Guangdong, P. R. China
2. Guangdong Provincial Key Laboratory of Colorectal and Pelvic Floor Diseases, The Sixth Affiliated Hospital, Sun Yat-sen University , Guangzhou, Guangdong, P. R. China
3. Department of Gastroenterology, Sir Run Run Shaw Hospital Affiliated to Zhejiang University , Hangzhou, Zhejiang, P. R. China