Fistula in ano.

Except for unusual diseases, fistula in ano originates from infection in the anal crypts of Morgagni, forming an abscess which, when it opens, results in a tract leading to the skin surface. A tentative diagnosis can often be made by a careful history followed by local examination. A history of para-anal abscess followed by intermittent discharge will almost always be elicited. Alternative causes, including especially Crohn's disease, are also described. Operative technique is described, including various methods for finding the internal opening and obscure branching tracts, as well as a number of pitfalls to be avoided.