[Perianal fistulas: developments in the classification and diagnostic techniques, and a new treatment strategy].

The aim of surgical treatment of perianal fistulas is to treat the patient's symptoms, with low recurrence rates and risk of incontinence. In recent years there have been developments regarding the classification and diagnosis ofperianal fistulas. MRI is the most appropriate diagnostic tool. In the hands of an experienced operator anal endosonography is a suitable, less expensive and readily-available alternative. As a result of developments in fistula surgery it is now more practical to classify perianal fistulas as low or high fistulas, as this has implications for the further treatment. Low perianal fistulas are defined as fistulas of which the fistula tract is located in the lower third of the external anal sphincter. High fistulas are fistulas in which the fistula tract runs through the upper two-thirds of the external sphincter muscle. Low perianal fistulas can be treated safely by fistulotomy. At present, rectal advancement is the gold standard for the surgical treatment of high transsphincteric perianal fistulas. The anal fistula plug might be an alternative for the treatment of high transsphincteric perianal fistulas.