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FISTUAL-IN-ANO

This is the commonest type of external fistula. It is lined by unhealthy granulation tissue and fibrous tissue, and has one end communicating with the perianal skin and the other end with the anal canal or with the rectum.

Origin:
Usually, it is sequelae to a perianal abscess, which has either been allowed to rupture spontaneously, or has been incised late or in an inadequate or incorrect manner. Occasionally, however, a fistula may be:
  • Tubercular
  • In associated with Crohn’s disease
  • A complication of carcinoma of the rectum
Classification and nomenclature:
  • The fistula may be classified as:
    • Extra-sphincteric, where the track lies immediately deep to the skin and mucous membrane
    • Trans-sphincter, where the track traverses through the fibers of the external and internal sphincters (commonest)
    • Subsphincteric, where the track passes entirely deep to both the sphincters (rare)
    • Pararectal (high-level), where the track passes deep to both the sphincters and then through the levator ani, to enter the rectum. This type, fortunately uncommon, is sequelae to pelvirectal abscess
  • The fistula may be:
    • Complete
    • Incomplete: Here the track ends blindly (this should be called a sinus). However, a minute internal opening should always be searched for
  • The fistula may be:
    • Single
    • Multiple: There is more than one external opening. In these cases there may be one or more internal openings. If there are multiple external fistulous openings, the condition is often termed Water-Can perineum
  • The fistula is called
    • Anterior or
    • Posterior
According to the position of the external opening: This is important in view of the Goodsall’s Rule; According to this rule, if the external opening of fistula is in relation to the anterior half of the anal opening, the fistula is straight, running radially into the anal canal. If, however the external opening is in relation with the posterior half of the anal opening the fistula is curved one, opening internally in the midline posteriorly, and often this is Horse-Shoe Fistula.

Clinical features:
There is a typical history of a perianal abscess, which, following rupture or incision fails to heal and leaves behind a discharging opening. If this is neglected, there are recurrent attacks of perianal abscess formation. The new abscess burst out either through the old openings. This is how multiple fistulae are formed.

Treatment:
Excision of the fistula is the only treatment.
  • For the commoner varieties of varieties of fistula (which are either extra-sphincteric or trans-sphincteric), the excision is fairly simple. A probe is passed in and, guided on it, a director. The track is now opened on the director. Thereafter:
    • either the unhealthy granulation tissue on the wall is fully scraped with a Volkmann’s spoon
    • Or, the whole track, with its fibrous tissue lining, is excised

      • The cavity is packed to heal subsequently by granulation.
  • For the subsphincteric variety (which is relatively less frequent) the above type of operation may lead to anal incontinence because the whole thickness of the sphincteric mechanism is cut through. In order to make a compromise between total excision of the track and maintenance of sphincteric activity, either of the following procedures may be adopted:
    • The lower part of the track, together with the superficial sphincteric fibres, is excised as above. A stout silk, threaded on the eye of a malleable probe, is now passed through the deeper part of the track, round the intact fibres of the sphincter and the anal canal mucosa, and is tied loosely. After about two weeks, at a second stage, the remaining part of the track, incorporated within the silk, is excised. Fibrosis, resulting from the previous operation, prevents retraction of the freshly cut sphincteric fibres, which later unite and again make up the sphincter (Gabriel’s two-stage operation)
    • Whole length of the metallic probe fistula must be opened. If the abscess, location is quite deep it is impossible to dissect great of mass of tissues and in this way from incised rectal gland abscess cavity we should ligate fistula and time by time tighten this ligature
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This article has been written by Dr. M. Javed Abbas.
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01:10 10/02/2003