[Classification and diagnosis of anal fistulas]

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...).