Anorectal abscess

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  • 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

  • Worsening pain around bowel movement, with decreased pain post rectal evacuation
  • Perirectal abscesses often accompanied by fever, leukocytosis
    • May only be paplpated via digital rectal exam
  • Tender inguinal adenopathy may be only clue to deeper abscesses

Differential Diagnosis

Anorectal Disorders


  • 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


  • All perirectal abscesses should be drained in the OR
  • All anorectal abscess requires surgical referral and followup
  • Common bacteria: Staphylococcus aureus, Escherichia coli, Streptococcus, Proteus and Bacteroides
  • 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 with out packing
    • Frequent sitz baths


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

Only indicated for:[1][2]

  • Elderly
  • Systemic signs (fever, leukocytosis)
  • Valvular heart disease
  • Cellulitis
  • Immunosuppression

Treatment options:


See Also

Anorectal Disorders

External Links

Rob Orman Lecture


  1. BMJ Best Practice Anorectal abscess
  2. - Practice parameters for the management of perianal abscess and fistula-in-ano.