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A study group was formed to undertake further investigation of the problems involved in the classification of anorectal anomalies. At first, a registration form including standardized techniques for clinical and roentogenologic investigation was defined, and then 254 cases were collected and analyzed by referring these materials to the International Classification by the Melbourne group in 1970. Our analysis disclosed: (1) It is imperative to establish a registration form with footnotes describing standardized techniques for clinical and roentogenologic investigations; (2) The rectourethral fistula has been classified simply as high type under the present International Classification, but differences in the levels of the rectal pouch and of the point of fistula, as observed in the collected materials, tends to show that further subdivision of this anomaly may be indicated; (3) An abnormal skin fold at the anal and/or perineal sites is not always diagnostic of low type, specifically of covered anus-complete. Conversely, some infants with high type anomaly had abnormal skin folds; and (4) Two types of anomaly, which have not been well described in the present classification, were detected. They were "rectal membraneous atresia" and "recto-penile fistula."

Parks' classification of the anal fistulas is based on the knowledge of the pathogenesis of the disease. It relates fistula tracks to the anatomy of the anorectal musculature. Four main types are described, with some variations in each group: inter-, trans-, supra- and extrasphincteric fistulas. A circumferential spread occurs in the horseshoe fistulas. Positive diagnosis of fistula is difficult when the secondary opening lies distant from the anus. Aetiological factors, topography of the tracks, and clinical form (benign or necrotizing fasciitis) are systematically established. Anal fistulas must be differentiated from other suppurations of the anorectal area: intestinal (tumours, actinomycosis, piles,...) and extravisceral diseases (pilonidal cyst, hidradenitis suppurativa, bartholinitis...).

This paper presents the application of a classification of anal fistulas to an unselected consecutive series of 793 patients treated for this condition at St Mark's Hospital from 1968 to 1973 inclusive. The fistulas were divided into five categories on their anatomical relationships: superficial (16 per cent), intersphincteric (54 per cent), trans-sphincteric (21 per cent), suprasphincteric (3 per cent) and extrasphincteric (3 per cent), with the remaining cases multiple or unclassified (3 per cent). There was good correlation between the categories and presentation, physical signs and treatment of the fistulas. Two hundred and forty-nine patients had potentially difficult fistulas. Follow-up of these patients revealed healing of almost all the fistulas, but the functional results were less satisfactory (incontinence of loose stool in 17 per cent and of flatus in 25 per cent, soiling in 31 per cent).

To evaluate the application of Parks' classification in the management of patients with fistula-in-ano, a study was undertaken to assess the outcome of surgery, especially with respect to the recurrence rate and alteration of continence. A retrospective analysis of 160 consecutive patients who were classified at the time of operation was conducted. The distribution of fistulas was as follows: intersphincteric, 41.9 percent, transsphincteric, 52.1 percent, suprasphincteric, 1.3 percent, extrasphincteric, 0. A horseshoe extension occurred in 8.8 percent of the fistulas and 3.8 percent did not exactly conform to the classification as they were either complex or combinations of more than one type of fistula. The sole immediate postoperative complication was bleeding, which occurred one week postoperatively and ceased spontaneously (0.7 percent). Alteration in continence occurred in 6 percent of patients with 2.6 percent experiencing temporary incontinence to flatus, 1.3 percent to liquid stool, and 0.7 percent to solid stool. Permanent loss of control for flatus occurred in one patient (0.7 percent) and for liquid stool in one patient (0.7 percent). No patients suffered loss of control for solid stool. Recurrence developed in 6.3 percent of patients, all between five and 25 months postoperatively. Classification was found to be a useful guide in the operative management of patients with fistula-in-ano.

A classification of anal fistulas is presented, which is the result of an analysis of 400 cases treated over the past 15 years, based on the pathogenesis of the disease and the normal muscular anatomy of the pelvic floor. Four main types were found but numerous variations of each occur, which are described. It is hoped that this will alert the surgeon to the various complex situations that he may encounter.

The pathology of anal fistulas was studied in 300 patients and a simple classification is put forward. Two main types of fistula are recognized: intrasphincteric and extrasphincteric, according to the relation of the track to the external sphincter. All fistulas start as a central space infection which either remains confined to the intrasphincteric compartment or spreads extrasphincterically. Intrasphincteric fistulas include both central and intersphincteric fistulas. The latter fistula, as well as the extrasphincteric, are either low or high according to the relation of the track to the levator plate. The classification is simple and practical. It clearly demonstrates the precise anatomic position of fistulas as related to anal musculature so proper planning for the treatment can be safely achieved.