One of the newest and most innovative medicinal approaches is cell therapy. Several clinical trials and experimental investigations have looked into the feasibility of treating CD-related fistulas with stem cells.

The current indication for ALOFISEL® (active ingredient: Darvadstrocel) is the treatment of difficult perianal Crohn's fistulas that have not responded well to at least one conventional therapy or biotherapy.

This brand-new cell therapy medication is created using amplified allogeneic human adult mesenchymal stem cells from adipose tissue (ADSC). The supplier mandates that two patients be booked for a single dose of ALOFISEL® due to the medication's expensive price-roughly €54,000 for a single dose of 120 million-which cannot be stored once thawed.

Only one of the two patients receives therapy; the other serves as the backup patient. By doing this, another "back-up" patient who might receive no care at all is avoided.

An developing alternate approach to allogeneic ADSC injection for the treatment of complicated anal fistulas in CD is autologous fat injection. In recent years, autologous fat grafts have been the subject of in-depth research. They are popular because it is simple to get clinical samples (lipoaspirate, adipose tissue), and because there are a lot of ADSCs in adipose tissue. Additionally, ADSCs show strong immunomodulatory and regenerative capacities.

We would wish to compare the effectiveness of these two injection kinds on perianal fistulas as part of our care of CD.

The trial will be made available to patients who are scheduled for perianal surgery with ALOFISEL® or backup (fat injection). The history and signs of perianal fistula will be noted if the patient doesn't object.

Two visits that correspond to typical follow-up visits for patients will be noted:

Visit following surgery: fistula clinical evaluation, analgesic use, etc. and six months after : clinical assessment, MRI

Inclusion Criteria:

• Complex anal fistula with the following criteria: - Inactive/slightly active luminal Crohn's disease under conventional treatment or biotherapy MRI has demonstrated effective drainage. Maximum of two internal orifices and three external orifices; persists despite internal orifice(s) closing.

Exclusion Criteria:

• Pregnant or breast-feeding women
• Patients hypersensitive to the product, bovine serum or any of the excipients of Alofisel
• Vulnerable persons: deprived of liberty, under guardianship, under curatorship, etc.

Population with Crohn's disease coming to the digestive surgery department of the CHU in Nantes for perianal surgery