Anorectal abscess

Background

• Usually begin via blocked anal gland (leads to infection/abscess formation)
  • Can progress to involve any of the potential spaces.

Finding	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

• Crohn’s disease
• Chronic constipation
• Diabetes mellitus
• Chronic corticosteroid use

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

• Anal tags
• Hemorrhoids
  • Internal hemorrhoid
  • External hemorrhoid
• Cryptitis
• Anal fissure
• Anal fistula
• Anorectal abscess
• Proctitis
• Rectal prolapse
• Rectal foreign body
• Pruritus ani
• Pilonidal cyst
• Constipation
• Condyloma acuminata
• Anal cancer
• Colorectal tumor
• Pedunculated polyp
• Crohn Disease
• Syphilitic fissure
• GC/Chlamydia

Evaluation

• 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

Management

• 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

Antibiotics

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

Only indicated for:

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

Treatment options:

• Ciprofloxacin 500mg PO bid and Metronidazole 500mg PO tid

See Also

Anorectal Disorders

External Links

Rob Orman Lecture

References

Authors

Ross Donaldson