The frequency of occurrence of ano-perineal fistulas, especially in the context of inflammatory bowel diseases, makes them a subject of growing interest, mainly because of the discomfort and medico-social impact they induce in patients who carry them. Their treatment depends on their extent and potential for evolution. MRI appears as the technique of first choice for their assessment and follow-up. After a brief technical review, we'll look at the anatomy and imaging assessment of ano-perineal fistulas in terms of inflammatory activity and healing, two important characteristics that could influence both the prognosis and the therapeutic strategy.