1 Department of Colorectal Surgery, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, P. R. China.
2 Department of General Surgery, The Second Affiliated Hospital of Harbin Medical University Harbin, Harbin, Heilongjiang, P. R. China.
3 Department of Gastrointestinal Surgery, Shenzhen Hospital, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shenzhen, Guangdong, P. R. China.