Comparison between magnetic resonance imaging and rigid rectoscopy in the preoperative identification of intra- and extraperitoneal rectal cancer.

Abstract Aim Accurate preoperative discrimination between extra-and intraperitoneal rectal cancer has important treatmentimplications. Our main objective was to compare thediagnostic performance of MRI with rigid rectoscopy(RRS) in assessing the location of rectal cancers above orbelow the peritoneal reflection (PR), using the findingsobtained during abdominal surgery for treatment of thecancer as the reference standard. We also compared theaccuracy of MRI and RRS in assessing the level of thelower border of the tumour from the anal verge.Method Patients with rectal carcinoma awaiting surgeryunderwent MRI and RRS. The MRI images werereviewed by two abdominal radiologists who determinedthe location of the inferior border of the tumour in rela-tion to the PR. Receiver–operating characteristics (ROC)curve analysis was performed to determine the diagnosticperformance of RRS at different cut-off values.Results The sensitivity and specificity were 98.15% and100%, respectively, for MRI, and 100% and 76.92%,respectively, for RRS at a cut-off value of < 10 cm. Themean level of the lower border of the tumour from theanal verge was 68 44.3 mm on RRS and73.5 42.4 mm on MRI (P = 0.25), with a trendtowards overestimation with MRI.Conclusion RRS is still the main means of assessing thelevel of a rectal tumour from the anal verge, but MRIhas value in determining the level of the tumour in rela-tion to the PR, which cannot be seen on endoscopy.Keywords Rectal cancer, rectoscopy, MRI, perito-neum, surgeryWhat does this paper add to the literature?To our knowledge, this is the first study focusing onthe comparison between the diagnostic performance ofMRI and rigid rectoscopy in assessing the location ofrectal cancer with respect to the anal verge and perito-neal reflection.