Preoperative MRI evaluation of mesorectum in cases of rectal carcinoma

Abstract

Objectives The aim of this study was to evaluate the accuracy of MRI in preoperative staging, in the prediction of negative circumferential resection margin (CRM), and in the planning of surgical management for rectal carcinoma. Background Rectal cancer constitutes about one-third of all gastrointestinal tumors. Preoperative imaging for staging of rectal cancer has become an important aspect of the current approach to rectal cancer management because it helps to select suitable patients for neoadjuvant chemoradiotherapy and determine the appropriate surgical technique. The purpose of this study was to assess the accuracy of MRI in the preoperative staging of rectal carcinoma, in the prediction of negative CRM, and for planning its surgical management. To this end we aimed to study its efficacy in preoperative local staging of rectal carcinoma (T and N stages), in evaluating mesorectal fat and fascia involvement, and in the prediction of negative CRM. Patients and methods Thirty-seven patients with pathologically proven rectal carcinoma underwent pelvic MRI on a 1.5 T magnet with pelvic phased array coil with transrectal gel administration. The MRI protocol was adhered to. All cases were operated upon and their postoperative specimens were compared with preoperative MRI results. Results Comparable to histopathological examination, MRI correctly diagnosed in 34 out of 37 patients in different T stages (accuracy 91.9%) and in 32 out of 37 patients in different N stages (accuracy 86.5%). Accuracy in the evaluation of mesorectal fat invasion was 97.3%, that in the evaluation of mesorectal fascia invasion was 94.5%, and that in the evaluation of CRM was 97.3%. Conclusion MRI of rectal cancer is accurate for preoperative staging, evaluation of mesorectal fat and fascia, prediction of negative CRM, and evaluation of lymph node involvement.