Anal Fissure Tổng quan về bệnh

Giới thiệu

An anal fissure is a linear tear within the anal canal usually extending from the dentate line toward the anal verge. This may occur at the posterior or anterior midline (primary) or be located in atypical, non-midline positions that warrant investigation for underlying conditions (secondary).

Dịch tễ học

Anal fissures commonly occur in younger and middle-aged adults. The peak incidence of anal fissure occurs between 15-40 years of age. It is estimated that the lifetime incidence of anal fissure is around 11%, with males and females being equally at risk. In the United States (US), there are as many as 230,000 to 342,000 new cases diagnosed annually.

Sinh lý bệnh

The anoderm, the epithelial lining of the anal canal (lies distal to the dentate line), is highly susceptible to microtrauma and tearing as a result of repetitive mechanical stress and/or increased intraluminal pressure. Anal fissures typically start here within the distal half of the anal canal. A tear then triggers cycles of pain and bleeding, leading to the formation of chronic anal fissure in about 40% of cases.

Anal Fissure_Disease Background

Nguyên nhân

Trauma during defecation, usually from the passage of hard stools or explosive diarrhea, is thought to set off anal fissure formation. Childbirth via vaginal delivery, anal intercourse, and anorectal surgery can also cause trauma to the anal canal. 

Phân loại

Acute versus Chronic Fissures

Acute fissures are simple splits or cracks in the anoderm present for <8 weeks. Fissures that have not healed after 8 weeks are considered chronic. Chronic fissures may show secondary changes (eg sentinel tag at the fissure’s distal aspect, hypertrophied anal papilla at the fissure’s proximal aspect, rolled edges, fibrosis of the edges or deep ulceration w/ exposure of the underlying internal anal sphincter muscle within the fissure’s base). This results from hypertonicity of the internal anal sphincter leading to local ischemia and impaired wound healing.