eMedicine Specialties > Emergency Medicine > Gastrointestinal

Anal Fistulas and Fissures

Author: Ingrid Legall, MD, Assistant Professor, Department of Emergency Medicine, Florida Hospital-Flagler
Contributor Information and Disclosures

Updated: Aug 18, 2009

Introduction

Background

An anal fissure is a superficial linear tear in the anoderm most commonly caused by passage of a large, hard stool. This tear is distal to the dentate line. Anal fissures are among the most common anorectal disorders in the pediatric population; however, adults also are affected.

An anal fistula is an inflammatory tract between the anal canal and skin. The 4 categories of fistulas, based on the relationship of fistula to sphincter muscles, are intersphincteric, transsphincteric, suprasphincteric, and extrasphincteric.¹

Pathophysiology

In anal fissures, anus distal to dentate line is involved. About 90% of anal fissures occur in the posterior midline where skeletal muscle fibers that circle the anus are weakest. The remaining 10% are found in the anterior midline.

Most anal fistulas originate in anal crypts, which become infected with abscess formation. When the abscess is opened or ruptures, a fistula is formed.

Sex

Anal fissures affect both sexes equally; however, an anterior fissure is more likely to develop in women (25%) than in men (8%).

• Anal fistulas are a complication of anorectal abscesses, which are more common in men than in women (male-to-female ratio of 2:1 to 3:1).
• Only 8% of anal fissures are anterior in men; 75-90% of fissures in women are posteriorly located.
• For reasons of intrinsic anatomy, rectovaginal fistulas are found only in women.

Age

Although anal fissures are the most common cause of rectal bleeding in infants, they are primarily seen in young adults.

• Eighty-seven percent of people with a chronic anal fissure are between the ages of 20 and 60 years old.
• Anal fissures in children may indicate sexual abuse.

Clinical

History

• Rectal pain, usually described as burning, cutting, or tearing
• Pain with bowel movements; spasm of the anus is very suspicious for an anal fissure.
• Bloody stools
  • Typically, bright-red blood appears on the surface of stools. Blood usually is not mixed into stool.
  • Occasionally, blood is found on toilet paper after wiping.
  • Patient may report no bleeding.
• Mucoid discharge
• Pruritus
• A patient with an anal fistula may complain of recurrent malodorous perianal drainage, pruritus, recurrent abscesses, fever, or perianal pain due to an occluded tract.
  • Pain occasionally resolves spontaneously with reopening of a tract or formation of a new outflow tract.
  • Pain occurs with sitting, moving, defecating, and even coughing.
  • Pain usually is throbbing in quality and is constant throughout the day.

Physical

• Start by optimizing patient placement; place the patient in the left lateral decubitus position with knees drawn up toward the chest.²
• Examine the patient carefully to avoid infliction of further pain or sphincter spasm. Examination may be facilitated by application of a topical anesthetic, such as Lidocaine jelly, prior to digital rectal examination.
• Most fissures are visible externally when the patient bears down as if having a bowel movement.
• Note the depth of the fissure and its orientation to the midline, often described using clock orientation of the hour hand.
• Most tears are found in the posterior midline.
• Rectal examination is generally difficult to tolerate because of sphincter spasm and pain.
• Acute fissures are erythematous and bleed easily.
• With chronic fissures, classic fissure triad may be seen.
  • Deep ulcer
  • Sentinel pile, which forms when the base of the fissure becomes edematous and hypertrophic (a resolving sentinel pile can result in a permanent skin tag or may become associated with a fistulous tract)
  • Enlarged anal papillae
• Bidigital rectal examination in a patient with a fistula-in-ano may reveal an indurated tract or cord.
  • Fistula can be identified by small circles of granulation tissue, which exude pus when compressed if tissue is patent.
  • A fistulous tract that opens internally can be visualized with aid of an anoscope.
  • Inguinal lymph nodes may be enlarged and painful.
• In an acute fistulous abscess, cardinal signs of inflammation, rubor, dolor, calor, and tumor (eg, erythema, pain, increased temperature, edema) may be found.
• Examination of the anus reveals a linear tear in fissure-in-ano.

Causes

• Passage of hard stool
• Chronic diarrhea
• Childbirth (accounts for 10% of chronic anal fissures)
• Habitual use of cathartics
• Anal trauma (can occur with anal intercourse or a rectal examination using a speculum or digit)
• Causes of anal fistula include opened perianal or ischiorectal abscesses, which drain spontaneously through these fistulous tracts.
• Anal fissures can be observed in patients with syphilis and other sexually transmitted diseases, tuberculosis, leukemia,³ inflammatory bowel disease such as Crohn disease, previous anal surgery, HIV, and other conditions or diseases.
  • Incidence of anal fissures in patients with leukemia is approximately 24%.
  • Fistulas are also found in patients with inflammatory bowel disease, particularly Crohn disease.⁴ The incidence of fissures in Crohn disease is 30-50%. Perianal activity often parallels abdominal disease activity, but it may occasionally be the primary site of active disease.
    
    

    

    Anal fistulas and fissures. This patient has a history of Crohn disease.

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    Anal fistulas and fissures. This patient has a history of Crohn disease.

     
  • Anal fistulas also are associated with diverticulitis, foreign body reactions, actinomycosis, chlamydia, lymphogranuloma venereum (LGV), syphilis, tuberculosis, radiation exposure, and HIV.
  • Approximately 30% of patients with HIV develop anorectal abscesses and fistulas.

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