Difficult fistulae.

Fistula in ano is a common disorder. The goals of treatment are to cure the fistula with minimal loss of sphincter function and with minimal healing time. Fortunately about 90% of fistulae are simple and obey Goodsall's rule. These fistulae are easily treated by the "lay-open" technique. Treatment can however become much more difficult with increasing complexity of fistula tracks, higher internal opening with major sphincter involvement, atypical and secondary tracks or at recurrence. Understanding of the anatomy and the pathogenesis of fistulae is mandatory to identify the fistula tracks and the internal opening and to tailor the treatment accordingly. Endoanal flap repairs and the use of setons are most widely accepted for the treatment of difficult fistulae but many other options exist. Underlying factors or associated diseases such as inflammatory bowel, AIDS and other sexually transmitted diseases, carcinoma, radiotherapy, hidroadenitis or other obscure infections may influence the final outcome and often demand a specific approach.