Groupe hospitalier Paris Saint-Joseph, Institut Léopold Bellan, Service de proctologie médico-chirurgicale, 185 rue Raymond Losserand, 75014 Paris
Groupe hospitalier Paris Saint-Joseph, Service de radiologie, 185 rue Raymond Losserand, 75014 Paris
Correspondance : V. de Parades
Anoperineal MRI is the gold standard to study anoperineal suppurations. Its prescription is essential for the management of recurrent or complex anal fistulas or if they are associated with Crohn’s disease. To obtain quality imaging, a minimal protocol is required comprising the following sequences like: Acquisition of T2-weighted sequences without fat saturation of the signal in the 3 planes of the anal canal (one of these sequences can be done with fat saturation of the signal), a 3D sequence or 3 2D sequences in the 3 planes of the anal canal in T1-weighting with fat saturation of the signal and after injection of gadolinium. A standardized report is useful to obtain a comprehensive analysis of anoperineal suppuration on MRI. The production of an anatomical diagram is appreciated by clinicians to guide the drainage of suppuration. The main etiology of anoperineal suppurations is crypto-glandular anal fistula. The anoperineal MRI is complementary to the proctologic examination to confirm or deny the relationship between the suppuration and the anal sphincter. It maps the fistula path with precision. It is useful to plan therapeutic strategy, especially for complex anal fistulas which require several anal surgeries with the placement of a seton. Finally, if necessary, it useful to check the effectiveness of the treatment. In fistulizing anoperineal Crohn’s disease, anoperineal MRI is essential before any surgery of an anal fistula except in an emergency context. In addition to the interests mentioned above, it is useful to distinguish disease-related inflammation from fibrosis and to assess the rectal wall. After the initiation of treatment with biotherapy ± an immunosuppressant in combination with surgery, MRI assess remission of the suppuration which is defined by the absence of collection > 10 mm and absent or moderate T2 hyperintensity of the fistula path and its extensions.