Background:The long-term management of perianal Crohn's disease for patients on anti-TNF-α therapy remains challenging. Aim: To evaluate the long-term course and complications of patients with perianal fistulas treated with anti-TNF-α based on their clinical remission and healing on MRI. Methods: Patients were evaluated clinically and by MRI. Deep remission was defined as clinical remission associated with the absence of contrast enhancement and T2 hyperintensity on MRI. Flare-free survival, surgery and hospitalizations were compared based on the presence or not of deep remission. Results: Forty-eight consecutive patients were included with a median follow-up of 62 months after anti-TNF-α first administration. Deep remission was observed in 16 patients (33.4 %). For patients in deep remission, the median time to any perianal event was 116 months (95-130) versus 42 months (8-72) in patients with pathological MRI (p < 0.001). Sixteen patients (50%) with pathological MRI had perianal surgery versus 2 (12.5%) in the deep remission group (p < 0.05). The mean duration of cumulative hospital stays was 0.75±0.52 days in the deep remission group versus 19.7±7.4 in the pathological group (p < 0.05).Conclusions: Higher flare-free survival and lower rates of surgery and hospitalization were found in patients achieving deep remission.

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