High intermuscular anal abscess and fistula: analysis of 25 cases

Although the majority of anal abscesses and fistulas are of the simple or low variety (intersphincteric or transsphincteric in Parks' classification), some of the simple, but high intermuscular, type are not recognized clinically and are not properly treated because they do not present the usual visible signs. Characteristically, there is no external swelling, induration or opening and there is high extension with a palpable mass or induration above the levator ani. Out of 350 patients with anal abscesses and fistulas treated by the first author, 25 (7%) patients had a high intermuscular abscess. Of these 25, 14 (56%) had a history of anal problems. Eight of these 14 had undergone anorectal surgery previously, and in 3 laparotomy was added, 2 being left with a diverting colostomy. On the other hand, 11 (44%) patients had no previous anal manifestation and 9 of them presented with an acute abscess. All patients had a palpable mass or induration above the levator ani and in all but one a primary opening was found on the dentate line. Fistulotomy was done in 22 of the 25 cases and incision and drainage into the anorectum in the other 3. The authors conclude that for prompt diagnosis and proper treatment the surgeon should be highly suspicious of the condition, have a perfect knowledge of the surgical anatomy of anal abscesses and fistulas and follow three steps: (a) look for a primary opening at the dentate line, (b) pass a cannula from this opening into the cavity or induration and (c) divide the circular muscle and internal sphincter until the upper end of the tract is reached.