Lunniss, Peter James; (1994) Aspects of fistula-in-ano. Masters thesis (M.S), UCL (University College London).

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Abstract

The cryptoglandular hypothesis as an explanation for the aetiology, pathogenesis and maintenance of idiopathic fistula-in-ano has been accepted yet hardly challenged since it was described over 30 years ago. The results of a prospective study of the surgical anatomy of acute anal sepsis are in accord with the hypothesis in that the demonstration of intersphincteric space sepsis is the most accurate predictor of an associated fistula. A histological study has also confirmed the importance of the ramifications of connective tissue from the intersphincteric space both as pathways for, and barriers against the spread of sepsis. However, the paucity of microorganisms which have been cultured or seen histologically in the intersphincteric component of chronic fistulae puts into doubt the central issue of chronic anal gland infection as the cause of fistula persistence. On the other hand, there is evidence that persistence may be related to epithelialisation, which need not be of anal gland type. The cryptoglandular hypothesis does not explain the observed gender difference in incidence; although no differences in circulating sex hormone concentrations between patients and controls were demonstrated, this does not mean that local endocrinological factors might not be involved. Successful management of fistula depends on accurate assessment. The inaccuracy of imaging techniques to date has meant that assessment has relied largely on clinical skill. A prospective study of the accuracy of magnetic resonance imaging has shown that for the first time, we have a non- invasive means of imaging fistulae which demonstrates pathology which may be missed at operation and which is the cause of recurrence. The superiority of MRI over endoanal ultrasound in imaging fistulae has also been demonstrated. A prospective study was performed to determine the effects of fistula surgery on continence and anorectal physiological variables. Contrary to widespread belief, postoperative disturbances of continence were found to be related more to internal sphincter division and reduced epithelial sensitivity than external sphincter division. Although lay open remains the surest way of eradicating pathology, surgery for all fistulae should be directed more to total sphincter preservation if incontinence is to be avoided.

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