Abstract:Objective To study the effect of the primary tumor MRI findings of stage T3 rectal adenocarcinoma on lymph node metastasis, and to improve the accuracy of the diagnosis of lymph node metastasis to guide the clinical selection of the best treatment scheme.Methods From May 2017 to May 2019,62 patients with stage T3 rectal adenocarcinoma confirmed by pathology at the First Affiliated Hospital of Jinzhou Medical University were collected. The imaging features were analyzed as follows: the location of the tumor, lesion length and thickness, the relationship between the center of the lesion and peritoneal reflection (hereinafter referred to as relationship with peritoneal reflection), the circumference of the lesion around the intestine, apparent diffusion coefficient (ADC) value, sub-classification of T3 rectal cancer and lymph node metastasis. The differences of imaging findings between the metastatic and non-metastatic lymph nodes groups were compared. The factors with statistical significance were included in the analysis of Logistic regression equation. The receiver operating characteristic curve (ROC) was used to obtain the critical value for predicting lymph node metastasis in stage T3 rectal adenocarcinoma.Results Comparison of the lesion thickness, the relationship between the center of the lesion and peritoneal reflection between the T3 stage rectal adenocarcinoma lymph node metastasis group, and the non-metastatic group showed statistically significant differences (P < 0.05). Multivariate Logistic regression analysis showed that the lesion thickness was independent predictor for lymph node metastasis [R = 13.343 (95% CI: 2.56, 69.64)]. The ROC curve showed that the critical value, sensitivity and specificity of lesion thickness for predicting lymph node metastasis in stage T3 rectal adenocarcinoma were 1.56 cm, 76.9% (95% CI: 0.564, 0.910), and 83.3% (95% CI: 0.672, 0.936), respectively.Conclusions The lesion thickness in MRI findings can be used as a preliminary to judge the lymph node metastasis of stage T3 rectal adenocarcinoma. It can improve the accuracy of diagnosis of lymph node metastasis and guide the clinic to determine the best treatment before operation.