An anal fissure is a superficial linear tear in the anoderm that is distal to the dentate line. Anal fissures are often associated with the passage of hard stools or anal trauma, but the exact etiology often remains unclear. Anal fissures are among the most common anorectal disorders in the pediatric population; however, adults are also affected.
Fissures are defined as acute if present for less than 6 weeks, and they are defined as chronic if present for more than 6 weeks.
An anal fistula is an inflammatory tract between the anal canal and the skin. The 4 categories of fistulas, based on the relationship of fistula to sphincter muscles, are intersphincteric, transsphincteric, suprasphincteric, and extrasphincteric.
An anal fistula can be categorized as either simple or complex. A simple anal fistula includes low transsphincteric and intersphincteric fistulas that cross 30% of the external sphincter. Fistulas are complex if the primary track includes high transsphincteric fistulas with or without a high blind tract, suprasphincteric and extrasphincteric fistulas, horseshoe fistulas, multiple tracks, anteriorly lying track in a female patient, and those associated with inflammatory bowel disease, radiation, malignancy, preexisting incontinence, or chronic diarrhea. Note the image below.