Biyan Lu1, Weibiao Ye2, Huanliang Liu3. 1. Guangdong Institute of Gastroenterology, the Sixth Affiliated Hospital, Guangzhou, China; Guangdong Provincial Key Laboratory of Colorectal and Pelvic Floor Diseases, Guangzhou, China; Institute of Human Virology and Key Laboratory of Tropical Disease Control of Ministry of Education, Sun Yat-sen University, Guangzhou, China; Dongguan Health School, Dongguan, China. 2. Dongguan Hospital of Southern Medical University, Dongguan, China. 3. Guangdong Institute of Gastroenterology, the Sixth Affiliated Hospital, Guangzhou, China; Guangdong Provincial Key Laboratory of Colorectal and Pelvic Floor Diseases, Guangzhou, China; Institute of Human Virology and Key Laboratory of Tropical Disease Control of Ministry of Education, Sun Yat-sen University, Guangzhou, China.