Utility of high resolution MRI for pre-operative staging of rectal carcinoma, involvement of the mesorectal fascia and circumferential resection margin

Abstract Aim of the work To assess utility of high resolution MRI for preoperative staging of rectal carcinoma, mesorectal fascia involvement and circumferential resection margin. Subjects and methods This prospective study included 40 patients (their mean age was 54.2 years). All patients were proved pathologically to have cancer rectum located about 15 cm from the external anal verge. MRI using high resolution sequences was done to all patients, then surgery was done, and MRI findings were correlated with pathological and surgical outcome. Results Twenty-five tumors were located in the upper rectum (62.5%), 7 in the mid rectum (17.5%), and 8 in the distal rectum (20%). MRI based T staging showed sensitivity, specificity, PPV and NPV of 95.8%, 87.5%,92% and 93.3% respectively with weighted kappa 0.84 and P_value 0.000. The sensitivity, specificity, PPV and NPV of MRI based assessment of circumferential resection margin (CRM) were 90.0%, 96.7%, 90% and 96.7% respectively with weighted kappa 0.86 and P_value 0.000. The accuracy, sensitivity, specificity, PPV and NPV of nodal staging by MRI were 85%, 73.3%, 92%, 84.6% and 96.7% respectively. Conclusion Preoperative MRI utilizing high resolution sequences is an accurate modality for pre-operative grading of rectal carcinoma, delineation of affection of the mesorectal fascia and circumferential resection margin which are the main factors affecting the outcome of surgery thus helping to categorize patients who can go directly for surgery from patients who may go for neo-adjuvant therapy to avoid overtreatment.