Anorectal Fistula

Introduction

• Description: An anorectal fistula involves communication between the anal or rectal canal and the perineum.

• Prevalence: Common. For women, 5.6/100,000 population. The male-to-female ratio is 1.8:1.

• Predominant Age: Any. The average age is late 30s to early 40s.

• Genetics: No genetic pattern.

Etiology And Pathogenesis

• Causes: Anorectal fistulae may spontaneously arise or result from the drainage of a perirectal abscess, most commonly an infected anal crypt gland. Patients with anal fistulae should be evaluated for the possibility of inflammatory bowel disease.

• Risk Factors: Although Crohn disease and tuberculosis are recognized risk factors, in most patients a predisposing cause is not apparent. Other risk factors include tears, puncture wounds, and internal hemorrhoids. Less commonly, carcinoma, radiotherapy, actinomycoses, tuberculosis, and chlamydial infections increase the risk. Up to 50% of patients with anal abscesses will develop a fistula.

Signs And Symptoms

• Intermittent perineal drainage or discharge

• Perianal lump or mass

• Pain (external sphincter) with defecation

• Anal bleeding

• Skin excoriation

• Most fistulae have the involvement of the posterior midline and origin in the anorectal crypts

Diagnostic Approach