Anal Fissure Disease Background

Introduction

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).

Epidemiology

Anal fissures commonly occur in younger and middle-aged adults, with increased frequency in those with chronic constipation. 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.

Pathophysiology

The anoderm, the epithelial lining of the anal canal lying 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. Hypertonicity of the internal anal sphincter reduces local perfusion causing ischemia, delayed healing and a self-perpetuating pain-induced spasm. A tear then triggers recurrent cycles of pain and bleeding, leading to the formation of chronic anal fissure in about 40% of cases.

Anal Fissure_Disease Background

Etiology

Primary Anal Fissure  

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 or anal intercourse can also cause trauma to the anal canal.  

Secondary Anal Fissure  

Secondary anal fissures are associated with previous anal surgeries, inflammatory bowel disease (IBD) (especially Crohn’s disease), gastrointestinal malignancies (eg colon cancer), and granulomatous diseases (eg tuberculosis [TB], sarcoidosis). Sexually transmitted infections may also manifest with anal fissure, along with discharge, perianal ulcers or fever. 

Classification

Classification of Anal Fissures

Acute anal fissures are simple splits or cracks in the anoderm present for <6 weeks. These fissures show sharply demarcated mucosal edges, occasional granulation tissue at the base and minimal fibrosis, indicating recent trauma. They often heal spontaneously within 4-6 weeks or with medical management, although approximately 40% will progress to chronic fissures. Fissures that have not healed after 6-8 weeks are considered chronic. Chronic anal fissures may show secondary changes: 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 with exposure of the underlying internal anal sphincter muscle within the fissure’s base. These are often harder to manage due to their tendency to recur.