Abstract:  ObjectiveTo investigate the value of endorectal ultrasonography (ERUS) and MRI examination in the preoperative evaluation of T staging and circumferential resection margin (CRM) of rectal cancer. MethodsThe retrospective cross-sectional study was conducted. The clinicopathological data of 193 patients ［122 males and 71 females, age (60±12)years with the range of 26-90 years］ who underwent radical resection of rectal cancer at the First Hospital of Jilin University from May 2016 to January 2018 were collected. All patients underwent ERUS and MRI examination before surgery, total mesorectal excision during surgery and postoperative pathological examination. Postoperative pathological results as the gold standard, the sensitivity, specificity in T staging and the CRM diagnostic coincidence rate of rectal carcinoma by ERUS and MRI examination are evaluated. Observation indicators: (1) evaluation of T staging of rectal cancer by ERUS and MRI examination; (2) evaluation of CRM in rectal cancer by ERUS and MRI examination. Measurement data with normal distribution were represented as Mean±SD. Sensitivity, specificity and coincidence rate were calculated by chi-square test of paired fourfold table. McNemar test was used to compare the coincidence rate of T staging between ERUS and MRI examination. Consistency between CRM measurement by ERUS examination and pathological examination of rectal cancer was conducted by Kappa analysis. Fisher exact probability test was used to compare the coincidence rate of positive CRM between ERUS and MRI examination. Results(1) Evaluation of T staging of rectal cancer by ERUS and MRI examination. The overall coincidence rate of T staging of rectal cancer and coincidence rates of T1, T2, T3, T4 staging by ERUS examination were 74.61% (144/193), 93.78% (181/193), 80.83% (156/193), 79.79% (154/193) and 94.82% (183/193), respectively. The sensitivity of T1, T2, T3 and T4 staging was 55.56% (10/18), 77.50% (31/40), 78.46% (102/130), 20.00% (1/5), and the specificity was 97.71% (171/175), 81.70% (125/153), 82.54% (52/63), 96.81% (182/188), respectively. The overall coincidence rate of T staging of rectal cancer and coincidence rates of T1, T2, T3, T4 staging by MRI examination were 50.78% (98/193), 90.67% (175/193), 74.09% (143/193), 58.55% (113/193) and 78.24% (151/193), respectively. The sensitivity of T1, T2, T3 and T4 staging was 0 (0/18), 17.50% (7/40), 68.46% (89/130), 40.00% (2/5), and the specificity was 100.00% (175/175), 88.89% (136/153), 38.10% (24/63), 79.26% (149/188), respectively. There was statistically significant difference between the overall coincidence rate of ERUS and MRI examination for T staging of rectal cancer (χ2=8.631, P<0.05). (2) Evaluation of CRM in rectal cancer by ERUS and MRI examination. The sensitivity and specificity of positive CRM evaluation of rectal cancer by ERUS examination were 100.00% (5/5) and 97.34% (183/188) respectively, and the coincidence rate with results of pathological examination was 97.41% (188/193), showing a high consistency between positive CRM evaluation of rectal cancer by ERUS examination and pathological examination (Kappa value=0.655, P<0.05). The sensitivity and specificity of positive CRM evaluation of rectal cancer by MRI examination were 40.00% (2/5) and 92.02% (173/188), and the coincidence rate with pathological examination was 90.67% (175/193), respectively, showing a high consistency between positive CRM evaluation of rectal cancer by MRI and pathological examination (Kappa value=0.206, P<0.05). There were statistically significant differences in the diagnostic coincidence rate and specificity of CRM positive evaluation for rectal cancer between ERUS and MRI examination (χ2=5.896, P<0.05). ConclusionERUS examination has a high coincidence rate in the preoperative T staging of rectal cancer and a high consistency between positive CRM evaluation of rectal cancer with pathological examination, which are superior to MRI examination in the two aspects.