To investigate the risk factors of lateral lymph node positivity in middle and low rectal cancer.

The data of 102 patients with middle and low rectal cancer who underwent laparoscopic radical resection and lateral lymph node dissection from January 1，2019 to December 30，2020 were retrospectively analyzed，and they were divided into positive group（n=21cases）and negative group（n=81cases）according to the lateral lymph node metastasis. The clinical data were statistically analyzed by SPSS 22.0 software，and the count data were expressed as［n（%）］，using χ² or Fisher's exact test. Logistic multifactor analysis was used for risk factors of positive lateral lymph nodes，and P<0.05 was considered as statistically significant difference.

A total of 1347 lateral lymph nodes were dissected in 102 patients with low and middle rectal cancer，and 8.1% of them were positive lymph nodes. Univariate analysis showed that age，tumor diameter，degree of differentiation，tumor type，T stage and degree of intestinal wall invasion were significantly correlated with the occurrence of lateral lymph nodes（P<0.05）. Logistic regression analysis showed that the degree of low differentiation，invasive type，T_3-4 stage and extrapserous tumor infiltrating intestinal wall were independent risk factors for positive lateral lymph nodes in low and middle rectal cancer（P<0.05）.

Low differentiation of tumor tissue，invasive cancer，tumor stage T_3-4 and infiltration of intestinal wall beyond serous membrane in patients with low and medium rectal cancer can be used as independent risk factors for lateral lymph node metastasis，and lateral lymph node dissection is recommended for patients with these risk factors.