Anal Fistulas in Severe Perineal Crohn's Disease: Mri Assessment in the Determination of Long-Term Healing Rates.

Background & Aims: The European Crohn's and Colitis Organization recommends magnetic resonance imaging (MRI) of anal fistulas to decide on the drug/surgery strategy. No evidence is available on the long-term impact of MRI features on fistula healing. The aim of this study was to evaluate the benefit of combined drug/surgery strategies for the treatment of perianal Crohn's fistulas based on MRI factors at referral.

Methods: The clinical event (anal abscess, new fistula tract, cellulitis), therapeutic intervention (introduction/optimization of immunosuppressant/biologics, anal surgery, intestinal resection, stoma), and MRI data were prospectively recorded for patients with Crohn's disease (CD) and anal fistulas. Healing was defined by fulfilment of all the following conditions: no discharge or pain, closure of the external opening of the fistula, no visible internal opening, no abscess, and no subsequent draining seton or drainage procedure performed during at least 1 year of follow-up.

Results: Seventy CD patients with anal fistulas and MRI evaluations were followed for 70 months. The cumulative rates of fistula healing were 25%, 40%, 50%, and 70% at 12, 24, 36, and 72 months, respectively. Severe, complex, branched, and high fistulas were associated with a less favorable outcome. Surgical closure of the tract improved the healing rates better than treatment with biologics or thiopurines. Male sex, A1 luminal phenotype, and anal ulceration at referral were independently associated with a higher healing rate.

Conclusions: Therapeutic strategies for perianal fistulizing CD require robust anatomical and healing evaluations. Combined strategies using biologics to improve both drainage and secondary closure of the fistula tracts merit further study.