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MRI is the gold standard in staging rectal cancer,predicting circumferential resection margin (CRM) involvement and the need forpreoperative radiotherapy (DXT). We assessed whetherpreoperative MRI couldpredict requirement for APR.We identified patients with rectal tumours below the peritoneal reflection. Preoperative MRI scans were examined by a radiologist blinded to eventual surgery. The anal sphincters were rated clear, equivocal or involved. MRIprediction and final surgicalprocedure were compared.Of 36 patients (24M, 12F, median age 69 (41-87)), 24 (66%) underwent LAR, 10 (28%) APR, and 2 (6%) a Hartmann'sprocedure (HP). 20 (56%) received DXT. MRI rated 28 cancers clear of the sphincters; 14 received DXT. Twenty-two patients underwent LAR, 2 HP and 4 APR. One had a positive CRM. Six were rated equivocal; four received DXT. Two underwent LAR and four APR. Two had a positive CRM. Two involved the sphincters radiologically; both had DXT then APR. One CRM was positive. Overall CRM was positive in 11% of these low rectal cancers. No patients undergoing LAR/HP had distal margin involvement.Although important inpredicting CRM involvement, MRI did not correctlypredict surgicalprocedure in 10 of 36 patients (28%) with low rectal cancer.