Long-term Follow-up of Anal Fistulae in Crohn's Disease Treated With Anti-TNFalpha and Interest of New MRI Sequences

Inclusion Criteria: * Aware and cooperative, giving written consent * Crohn's disease diagnosed with clinical, biological, endoscopic and/or radiologic criteria * Patient treated with infliximab or adalimumab for perianal fistulizing Crohn's disease since at least one year * Absence of drainage seton at inclusion * Absence of active perianal lesions at inclusion: absence of suggestive symptoms and normal proctologic clinical examination without general anesthesia * Patient with MRI monitoring for perianal fistulizing Crohn's disease Exclusion Criteria: * Patient under juridical protection or without affiliation to social security * Refusal or impossibility of giving informed consent * Patient not followed-up by MRI or having a contraindication for MRI, especially the presence of cardiac stimulators or implantable defibrillators, cochlear implants, neurosurgical clips, intra-orbital or encephalic metallic foreign bodies, endo-prostheses placed since at least 4 weeks or osteosynthesis material placed since less than 6 weeks or gadolinium intolerance history * Surgery for Crohn's disease already planned at inclusion visit, individual participating to another study evaluating efficacy and/or tolerance of medical or surgical treatment for perianal fistulae of Crohn's disease * Patient treated with anti-TNF for luminal Crohn's disease * Patient having active perineal lesions