Diagnostic accuracy of MRI in mesorectal fascial involvement

Introduction: Evaluation of mesorectal fascial involvement in rectal cancer is of prime importance in decision making regarding treatment options. Objective: To determine diagnostic accuracy of Magnetic Resonance Imaging (MRI) in detection of mesorectal fascia involvement in rectal carcinoma patients using histopathology as gold standard. Materials & Methods: A comparative study was performed in the Radiology department of Kuwait Teaching Hospital, Peshawar, from January 1, 2021, till December 31, 2021, on 155 patients of rectal carcinoma who had their MRI done for rectal cancer on 0.3T MR Machine. Surgical findings like mesorectal fascial involvement by the tumor, presence/absence of pelvic lymph nodes within 5mm of mesorectal fascia, and staging of the tumor were included as variables. Specimens were sent in formalin to a histopathologist, and findings were considered for comparison. Data were analyzed using SPSS version 23. Results: Out of 155 patients, 82 patients showed mesorectal fascial involvement whereas 73 patients were Circumferential Resection Margin (CRM) negative. Out of these 7 patients were falsely labeled as CRM positive on MRI, whereas 9 patients were falsely labeled as CRM negative on MRI. Positive predictive value was 91%, with negative predictive value of 88%. Diagnostic accuracy was 89.6%. Sensitivity was 89% whereas specificity was 90.4%. Conclusion: MRI has high sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy for detection of mesorectal fascial involvement in case of rectal carcinoma taking 5mm as cut off value.