Classification of anal fistulas based on clinicopathological evidence

ABSTRACT

Multiple classifications for anal fistulae are available in the literature, but unfortunately, non of them gained a universal acceptance. The present study aimed at a long term evaluation of a simple classification for anal fistulae based on clinical and pathological evidence and depending primarily on the site of the internal opening. 400 patients with anal fistulae seen during the last 10-years [1990 - 2000] in Alexandria city were included in the present study. Detection of the internal and external openings, together with maping of the fistulous tracks in relation to the anal sphincter complex were done to every case, and operation was planned accordingly. Cases were divided according to the classification suggested in this study. The external openings varied from 1-4, were located up to 8cm. from the anal verge, were commonly posterior and lateral, and were absent in 7.25% of cases. The internal openings were detected in all cases during operation by a variety of means, and was located at the dentate line in all cryptoglandular anal fistulae [92%], above the dentate line in high and extrasphincteric anal fistulae in [2.75%], and below the dentate line in low anal fistulae in [5.25%]. Internal openings were commoner posteriorly and laterally than anteriorly. Trans-sphincteric anal fistulae were the commonest [53%], with high blind tracks in 12.3%. 10 cases were trans-sphincteric horse shoe fistulae [7 posterior and 3 anterior]. Intersphincteric anal fistulae were seen in [38%], with high blind tracks in 5.3%. Suprasphincteric anal fistulae was the rarest [1%], and all showed high blind tracks. Extrasphincteric anal fistula was seen in [1.5%], with high blind tracks 66.7%. High anal fistulae in [1.25%], with high blind tracks in 60%. Low anal fistula in [5.25%]. Based on the pathogenesis and the site of the internal openings relative to the dentate line, anal fistulas could be classified into two major groups; the crypto glandulars and the non-cryptoglandulars. The Cryptoglandular anal fistulas [92%] possessed their internal openings almost always at the dentate line, and included; intersphincteric, trans-sphincteric and suprasphincteric types, as anatomically described by Parks. The Non-crypto glandular anal fistulas [8%] included anal fistulas with their internal openings either above the dentate line [the high and the extrasphincteric anal fistulas], or below the dentate line [The low anal fistulas]. Different varieties exist under each type according to the ramifications taken by the fistulous tracks. This proposed classification was found to be simple, applicable, reproducable, respects the pathogenesis, and proved to be of help with operative treatment