MR T2 WEIGHTED ASPECT OF PERIANAL FISTULA S

Introduction: Anal fistulae are pathological conditions observed in in fections of the Hermann and Defosses' glands or related to Crohn's dis eases. The success and the lack of complication of surgical treatment depends on how accurately the tracks are assessed. The contribution of MRI in anal fistulas is now well established but the imaging appearan ce is not well discribed. The purpose of this work was to discribe the different patterns of lesions. Material and methods: Eighteen patient s with anal fistulas were examined with MRI before operation (mean del ay: 14 days. range: 1-56). SE T2 sequences, in coronal and axial plane s referred to the anal canal were performed. The examinations were rev iewed and compared with the results of surgical assessment to correlat e imaging and surgical findings. Results: Lesions were hyperintense on T2-weighted sequences but were also iso- or poorly hyper-intense when they did not contain fluids but only inflammatory tissue. When involv ing the supra-levator space, lesions were nodular. They were well limi ted if they occurred in the supra-levator space itself. On the contrar y, the rectal wall was thickened and hyper-intense when the fistulous tract reached it. Lesions were similar in Crohn's disease, except for anal fissures which were seen as a tubular hypersignal in contact with the anal lumen. On T2 sequences, healed fistulas were not visible. Co nclusion: The simple SE T2 sequences can discriminate between differen t patterns of lesions, especially for supra-levator extensions, fissur es in Crohn's disease and chronic inflammatory lesions without fluid. The use of more recent machines or fat suppression sequences may impro ve the detectability of lesions, especially the more chronic ones.