Inclusion Criteria:  high trans-sphincteric fistulas fistula confirmed and classified by an MRI. seton (> 6 weeks) prior to fat injection informed, written consent.  Exclusion Criteria:  Anovaginal fistula  Active sepsis IBD, immunodeficiency, prior pelvic irradiation and malignancy Insulin dependent diabetes More than 4 prior attempts of fistula closure Tobacco smoking or nicotine substitution 8 weeks prior to fat injection. Pregnancy Psychiatric disorders BMI ≥ 35 or BMI<20 Active tuberculosis Patient less than 18 years Unable to undergo MRI