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Abstract
The fistula is an abnormal communication between two epithelial lined surfaces; it is lined by granulation tissue that is why it persists. The cryptoglandular hypothesis is the most accepted theory in the pathogenesis of the anal fistulae, also there are some other causes e.g. Crohn’s disease, ulcerative colitis, tuberculosis, actinomycosis, foreign body, lymphograuloma venereum and trauma.
The estimated incidence among population is about 1:10.000 and male to female ratio is of between 2:1 and 4:1.
In the standard classification of anal fistulae, the fistulae are classified into two groups; low level fistulae in which the internal opening below the anorectal ring, and high level fistulae in which the internal opening at or above the anorectal ring, but the most widely used classification is that of Parks’ in which the anal fistulae are classified into; intersphincteric fistulae in which there are simple and complicated, trans-sphincteric fistulae in which there are simple and complicated, suprasphincteric fistulae and extrasphincteric fistulae.