Anography: a technique for determining the location of the internal opening in perianal fistula

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AimAnography is a radiological investigation for fistula-in-ano that identifies the primary fistula track through the internal opening. The efficacy of anography as a radiological method of identifying the location of the internal opening was investigated.MethodA retrospective study of 50 patients with a clinical diagnosis of fistula-in-ano of criptoglandular aetiology was performed. During anography, the location of the internal opening was recorded with respect to the quadrant of anal canal and distance from the anal verge. These data were compared with the findings during examination under anaesthesia (EUA), which was used as the gold standard for the identification of the internal opening.ResultsThe sensitivity of anography for identifying a patent internal opening was 91% and specificity 100%. There was complete agreement between anography reports and findings at EUA regarding the quadrant of anal canal in which the internal opening was located. In more than 90% of patients, the internal opening was found at EUA within 1 cm from the site described on anography.ConclusionAnography is an accurate test for predicting the exact quadrant of the anal canal in which the internal opening is located, as well as the distance of the internal opening from the anal verge. This inexpensive and simple radiological investigation should be the test of first choice in the evaluation of patients with fistula-in-ano when difficulty is anticipated in identifying the internal opening.

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