Anorectal Abscess



  • Localized induration, inflammation, and infection of the cryptoglandular tissues of the anal canal
  • 80% are perianal; the remainder are intrasphincteric or supralevator.
  • On clinical continuum with anorectal fistula, chronic or recurrent infection predisposes to fistula formation.
  • System(s) affected: gastrointestinal, skin/exocrine
  • Synonym: perianal abscess; perirectal abscess

Geriatric Considerations
A high pelvirectal abscess may cause minimal symptoms (lower abdominal pain and fever).

Pediatric Considerations
Common in 1st year of life


  • Predominant age: all ages (most common in 3rd and 4th decades and during infancy)
  • Predominant sex: male > female (2 to 3:1)


Etiology and Pathophysiology

  • Bacterial invasion of the anal glands found in the intersphincteric space, which may begin with an abrasion or tear in lining of anal canal, rectum, or perianal skin
  • The internal anal sphincter serves as a barrier to infection between gut lumen and perianal tissues.
  • Four types: Perianal (perirectal) is the most common (60%). Ischiorectal is the next most common followed by intersphincteric and supralevator (1)[C].
  • Organisms (usually mixed aerobic; anaerobic)
    • Escherichia coli
    • Streptococci
    • Staphylococci (especially methicillin-resistant)
    • Bacteroides fragilis
    • Pseudomonas aeruginosa

Risk Factors

  • Inciting trauma
    • Injections for internal hemorrhoids
    • Enema tip abrasions
    • Puncture wounds from eggshells or fish bones
    • Foreign objects
    • Prolapsed hemorrhoid
  • Inflammatory bowel disease
  • Chronic granulomatous disease (especially Crohn disease)
  • Immunodeficiency disorders
  • Hematologic malignancies (5–8% have anorectal abscess at some time)
  • Diabetes mellitus
  • Chronic medical immunosuppression
  • Morbid obesity

General Prevention

  • Avoid constipation.
  • Avoid rectal thermometers, enemas, or suppositories whenever possible in immunocompromised patients.

Commonly Associated Conditions

  • Crohn disease
  • Other inflammatory disease (e.g., appendicitis, salpingitis, diverticulitis)
  • Consider perianal hidradenitis suppurativa or HIV disease in patients with recurring perianal or ischiorectal abscesses.
  • Consider anal fistula in patients with recurrent perianal abscesses in same location.

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