Description

• 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

Epidemiology

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

Incidence
Common

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.