Autologous Stem Cells Derived From Lipoaspirates for the Non-Surgical Treatment of Complex Perianal Fistula

Inclusion Criteria: * Patients of both sexes older than 18 years of age. * Patients with a complex perianal fistula pathology which we define as the subjects that fulfil some of the following conditions: * No palpation of the fistula tract beneath the perianal skin. * A tract that is parallel to the rectum on exploration with a stylet. * Associated faecal incontinence. * Risk factors of anal incontinence. * At least one previous operation for a fistulous disorder. * Suprasphincteric trajectories * Rectovaginal fistula * Prior diagnosis of Crohn's disease. * Patients from whom written informed consent has been obtained for them to participate in the study prior to performing any procedure described in the study. * Patients that have already been subjected to a colonoscopy within a period of up to 6 months prior to the study. Exclusion Criteria: * Patients that are extremely thin who should not be subjected to liposuction. * Known allergy to local anaesthetics or to bovine proteins * History of neoplasia in the past 5 years. * Patients with a diagnosis of active Tuberculosis at the moment of inclusion. * Patients with prior positive markers for any of the following pathogens: Hepatitis B and C, HIV-1 or HIV-2. * Any other medical condition that in the judgement of the investigator could interfere with their optimal participation in the study or produce a significant risk to the patient. * Patients that have participated in another study in the 30 days prior to this one or that have planned to participate simultaneously in another study. * Patients that have not given their informed consent to participate in this study. * Psychiatric disorder or other factors that in the judgement of the investigator could complicate the participation of the patient in the study. * Breast feeding, gestation or intention to become pregnant up to 6 months after finalising their participation in the study, or that are not using adequate methods of contraception during the same period.