1 Department of Colorectal Surgery, 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 Guangdong Institute of Gastroenterology, Guangzhou, Guangdong, P. R. China.
4 Department of Anesthesiology, the Sixth Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong, P. R. China.