Ano-perineal (or ano-rectal) fistulas are a frequent and major complication of Crohn's disease. Indeed, they indicate a greater severity of the disease. In addition, they have a major impact on the quality of life of patients. Finally, these fistulas are difficult to cure, especially when they are complex. Indeed, medical treatment with anti-TNF drugs can only cure them in one third of cases. Various obturation treatments have been proposed in addition to medical treatment such as advancement flap, injection of biological glue, placement of a plug, intersphincter ligation of the fistulous path or laser but with still insufficient healing rates.

The injection of mesenchymal stem cells of adipose origin was first proposed for this indication in 2003. Since then, numerous studies have been published on the subject. Most importantly, an international multicenter randomized double-blind phase 3 controlled trial demonstrated the superiority of allogeneic stem cells over placebo with a therapeutic effect maintained at one year follow-up. The trial involved selected patients with Crohn's disease and one or more complex ano-perineal fistulas refractory to conventional treatments. This treatment has a high cost and its practical modalities are constraining (manufacturing, delivery, constrained time between the factory and the injection). However, this study is the first to have demonstrated in such a rigorous way the effectiveness of a local treatment on complex ano-perineal fistulas of Crohn's disease. These allogeneic mesenchymal stem cells have therefore been granted marketing authorization in Europe and have been commercialized in several European countries including France during the summer of 2020 under the trade name ALOFISEL®. They are indicated for complex ano-perineal fistulas that have not responded to at least one conventional biological treatment, in the context of inactive or less active Crohn's disease.

The main objective of the study is to evaluate the rate of "deep" remission (i.e. clinical and radiological) at 12 months of follow-up in the first patients treated in France with ALOFISIEL® after its marketing. The evaluation is performed at 12 months because it seems that the result is consolidated after this period.

Inclusion Criteria:

• Patient whose age ≥ 18 years
• Patient with inactive or minimally active Crohn's disease associated with one or more complex ano-perineal fistula(s) that has not responded to at least one conventional biologic therapy
• Patients managed for their fistula(s) by mesenchymal stem cell injection between July 1, 2020 and July 30, 2021 at one of the participating centers
• Patients who understand the French language

Exclusion Criteria:

• Patients under guardianship or curatorship
• Minor patients
• Pregnant women
• Patient deprived of liberty
• Patient under court protection
• Patients who object to the use of their data for this research
• Patients with a simple anal fistula
• Patients with anorecto-vaginal fistula
• Patients with anal canal stenosis that cannot be crossed by the index finger
• Patients who have not previously received medical treatment (biotherapy +/- immunosuppressant)

Patient with inactive or minimally active Crohn's disease associated with one or more complex ano-perineal fistula(s) that has not responded to at least one conventional biologic therapy, managed for their fistula(s) by mesenchymal stem cell injection between July 1, 2020 and July 30, 2021 at one of the participating centers.