Diagnostic Accuracy of Rectal Tumor Staging MRI in Evaluating Extramural Vascular Invasion

Aim: To determine the diagnostic accuracy of baseline pre-operative MRI in detecting extramural vascular invasion in rectal tumors compared with histopathological reference standard. Materials and Methods: Patients presenting with rectal carcinoma at Salmaniya Medical Complex, Bahrain between 1 st January 2017 and 31 st December 2019 were retrospectively reviewed for the presence of extramural vascular invasion (EMVI) detected on pre-operative staging MRI and a 5-point EMVI score (0-4) was assigned. These findings were then correlated with histopathology reports that were labelled as either positive or negative for EMVI. Results: A total of 82 patients were included in this study. Out of these patients, 71 patients (86.5%) received pre-operative chemotherapy and radiotherapy. 11 patients (13.4%) did not receive any pre-operative chemotherapy or radiotherapy and proceeded directly to surgery. On MRI EMVI (mr-EMVI) was reported in 31 patients (37.8%) while on pathology it was seen in 26 patients (31.7%). Sensitivity, specificity and accuracy of mr-EMVI were 81.2%, 90% and 86.6%, respectively. It was noted that upon staging the tumor, the stage most frequently associated with EMVI was Stage T3c with 18 out of the 31 cases (58%) showing EMVI on MRI. The predominant location of the tumors showing mr-EMVI was in tumors located in mid rectum (90.3%; 28/31). Conclusion: Pre-operative baseline MRI for staging rectal tumors is a highly effective imaging modality to evaluate for the presence of EMVI which can have a significant effect on the management plan.