Abstract: Objective To compare the diagnosis values of endorectal ultrasound (ERUS) and magnetic resonance imaging(MRI) in differentiating benign from malignant tumors of rectal and in preoperative staging of rectal cancer. Methods A retrospective analysis was conducted on 76 patients with rectal tumor diagnosed and confirmed by pathology in Xuanwu Hospital from May 2015 to June 2019. All patients underwent ERUS and MRI examinations from 7 to 10 days before surgery. Pathological results indicated 33 patients with benign tumor and 43 patients with malignant tumor. The gold standard of pathological diagnosis was used to compare the diagnostic value of ERUS and MRI in the differentiating of benign and malignant rectal tumors and the depth of rectal cancer invasion (T staging) and regional lymph node metastasis (N staging). Results Out of a total of 76 patients, 72 rectal tumors were analyzed with ERUS, because of 4 cases of enteric stenosis or undetectable. MRI was performed on 76 patients with rectal tumor. The sensitivity, specificity and accuracy of ERUS in rectal cancer diagnosis were 90.6%, 90.9% and 90.8%, respectively, while those of MRI in rectal cancer diagnosis were 83.7%, 87.9% and 90.2% respectively. There was no statistical difference between the two methods. TN staging analysis was performed on 43 patients with MRI, while 39 patients with ERUS, due to 4 patients with enteric stenosis or undetectable. The results showed that the accuracy of ERUS in judging stages of T1, T2 and T3 was slightly higher than MRI (92.3% vs 88.3%,82.1% vs 74.4%, and 87.2% vs 86.0%, respectively). The accuracy of ERUS in judging T4 staging was lower than MRI (97.4% vs 100%). The total accuracy of T staging with ERUS was higher than that with MRI (79.5% vs 74.4%), without statistically significant difference. The accuracy of N staging with ERUS was lower than that with MRI (61.5% vs 74.5%), with statistically significant difference. Conclusion MRI and ERUS show respectively advantages in T and N stages. Both MRI and ERUS have high accuracy in the differential diagnosis of benign and malignant rectal tumors, without statistically significant difference. For patients with T1, T2 and T3 stages of rectal cancer, the first choice is row ERUS, while MRI is the first choice for the evaluation of patients with T4 stage rectal cancer and lymph node metastasis around the rectum.

Key words: rectal neoplasms, endosonograph, magnetic resonance imaging