• Patients with complex fistulas

• Complex fistulas include trans-sphincteric fistulas involving more than 30% of the external sphincter, supra-sphincteric fistulas, extra-sphincteric fistulas, horseshoe fistulas, fistulas involving multiple tracts (according to the ASCRS) and fistulas with a curved tract or a tract presenting diverticula, for which:

• Suppuration is described by the patient and/or visible by an opening in the anal margin or by anoscopy Clinical symptoms led to an MRI demonstrating the path Fistula path demonstrated in the acute phase during drainage of an abscess

• Patient ≥ 18 years at study entry

• Patients with a previously drained fistula, without diverticula \> 10 mm, without T2 hyperintensity (assessed by MRI). Drainage is achieved by placing a seton, usually from 10 weeks to 12 months prior to the procedure

• Patient and investigator signed and dated the informed consent form prior to the procedure