Anorectal abscess


Anorectal abscess types and their locations.
  • Usually begin via blocked anal gland (leads to infection/abscess formation)
    • Can progress to involve any of the potential spaces.
Perianal Ischiorectal Intersphincteric, deep postanal, pelvirectal
Epidemiology Most common Second most common Least common
Symptoms Located close to anal verge, posterior midline, superficial tender mass Larger, indurated, well-circumscribed, located laterally on medial aspect of buttocks Rectal pain, skin signs may not be present
Comments High incidence of fistula formation even with drainage Constitutional symptoms often present

Risk Factors

Clinical Features

Perianal abscess.
Perianal abscess.
  • Worsening pain around bowel movement, with decreased pain post rectal evacuation
  • Perirectal abscesses often accompanied by fever, leukocytosis
    • May only be palpable via digital rectal exam
    • Perianal abscesses typically do not cause fever in immunocompetent individuals
  • Tender inguinal lymphadenopathy may be only clue to deeper abscesses

Differential Diagnosis

Anorectal Disorders

Skin and Soft Tissue Infection



  • CT with IV contrast can be useful to define deep abscesses (especially with pain out of proportion to exam)
  • May consider ultrasound or MRI as alternatives


  • Isolated perianal abscess is only type of anorectal abscess that should be treated in ED
    • Consider either linear incision with packing, elliptical incision, or cruciate incision without packing
    • Frequent sitz baths
  • All perirectal abscesses (ischiorectal, intersphincteric, supralevator) should be drained in the OR
  • All anorectal abscesses require surgical referral and follow up


Causative organisms: Mixed infection with fecal flora for anaerobes and Gram Negatives (Bacteroides fragilis and Escherichia coli)

Use is controversial

Treatment options:



  • Perianal abscess

See Also

External Links


  1. BMJ Best Practice Anorectal abscess
  2. - Practice parameters for the management of perianal abscess and fistula-in-ano.
  3. Mocanu V, Dang JT, Ladak F, et al. Antibiotic use in prevention of anal fistulas following incision and drainage of anorectal abscesses: A systematic review and meta-analysis. Am J Surg. 2019;217(5):910-917.