Tissue Therapy of Transsphincteric Anal Fistula

Inclusion criterion: Adult patients (\>= 18years) with complex anal fistula (high transsphincteric or suprasphincteric), with involvement of more 30% of the anal sphincter referred to the surgical department at Odense University Hospital for treatment, and who are: * able to communicate with Danish language * able to provide informed consent * having address in the region of southern Denmark during the study Exclusion criteria: 1. Signs of suppuration/cavitation around the fistula 2. Simple or low anal fistula, which can be treated by simple surgical incision 3. Ano-vaginal and recto-vaginal fistula 4. The presence of more than one fistula tract, more than two external orifices or more than one internal orifice 5. Inflammatory Bowel Disease 6. Immunosuppression (due to clinical condition or medical therapy) 7. Malignancy within 5 years 8. Previous radiotherapy of the abdomen and pelvis 9. BMI under 18.5 10. Allergy against the antibiotics: Penicillin and streptomycin. 11. Coagulopathy 12. Pregnancy and lactation (positive HCG (human chorionic gonadotropin) test) 13. Verified syphilis, HIV, or hepatitis on screening test