The study aims to evaluate effectiveness of the association of endorectal advancement flap technique with local injection of autologous and micro-fragmented adipose tissue, obtained with the Lipogems® system, in patients with complex Perianal Fistulas not related to Crohn's Disease.

Treatment of anal fistula pursues permanent healing and preservation of anal continence, not always easy goals in complex anal fistulas.

In patients with Crohn's disease, simple surgery (ligation of the path and suturing of the internal orifice) associated with injections of stem cells derived from autologous or allogeneic adipose tissue has been shown to cure up to 70%. of the cases. Similar results have been obtained in small series of patients with fistulas of cryptoglandular origin and also in rectourethral and rectovaginal fistulas of other etiologies. Unfortunately, this treatment is time consuming and extremely expensive.

Fresh adipose tissue is an alternative source of mesenchymal stem cells (MSC) with regenerative capabilities, immunomodulatory angiogenic and anti-inflammatory effects. The injection of fresh adipose tissue, obtained by liposuction from the same patient, is currently a therapeutic alternative used in regenerative medicine, plastic and orthopedic surgery indications, as well in other fields. Beneficial effects of fresh adipose tissue on anus fistulas and fecal incontinence have also been reported.

The aim of the present study is to evaluate the effectiveness of the injection of autologous, microfragmented and minimally manipulated adipose tissue, associated with a surgical technique that obtains by itself up to 70% cure in order to add the benefits of surgery with those in regenerative medicine hoping that the beneficial effects of MSC will aid in the healing and repair process.

A prospective study is proposed in 12 patients with non-Crohn's-related complex anals fistulas. Whenever possible, the endorectal advancement flap technique will be applied; in blind fistulas and special cases, in which the flap is not indicated, alternative techniques will be used. In all cases, autologous, micro-fragmented and minimally manipulated adipose tissue, obtained with a standardized procedure, previously validated and authorized, will be injected. This procedure uses the "Lipogems ®" device (Lipogems International SpA, Milan, Italy), with which a well-characterized adipose tissue is obtained with the maximum safety guarantees.

Inclusion Criteria:

• Patients of both genders, aged over 18 years old.
• Diagnosis, confirmed by standard methods (magnetic resonance and/or trans-anal ultrasound), of complex fistula (trans-sphincteric unsuitable for treatment lay-open).
• Seton placed at least 4-6 weeks previously.
• No limitations to a periodic follow-up lasting for a total of 12 months
• Informed consent form signed.

Exclusion Criteria:

• Active septic process.
• Patients unable to follow the pathway required by the protocol.
• Pregnant women.
• Failure to sign the informed consent form