S3 guidelines: cryptoglandular anal fistulas. German Association of Scientific Medical Societies (AWMF) registry number: 088/003

Background. With an incidence of 2 in 10,000/year, fistula-in-ano of cryptoglandular origin is a common disease, affecting predominantly young males. Incorrect treatment can adversely effect quality of life, particularly in terms of stool continence. Methods. A systematic review of the literature has been undertaken. Results. Since relevant randomized studies are scant, the level of evidence is low. The classification of anal fistulas depends on the relation between fistula channel and anal sphincter. Anamnesis and clinical examination are sufficient to establish the indication for surgery. In addition, an intraoperative probe and/or staining of the fistula channel should be performed. Endoanal ultrasound and magnetic resonance tomography are similar in predictive value. These modalities may be able to provide additional information in complex fistulas. The treatment of anal fistulas consists of one of the following surgical procedures: lay-open technique, seton drainage, plastic reconstruction with suture of the sphincter or occlusion with biomaterials. The lay-open technique should only be performed in superficial fistulas. The risk of impaired postoperative continence increases with the thickness of the divided sphincter muscle. A sphincter-saving procedure should be undertaken for all high anal fistulas. The results of the different techniques using plastic reconstruction are largely comparable. A lower healing rate is seen with occlusion using biomaterials. Conclusion. This clinical S3 guideline provides instructions for the diagnosis and treatment of cryptoglandular fistula-in-ano for the first time in Germany.