Anorectal abscess

Background

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

Perianal

• Most common
• Located close to anal verge, posterior midline, superficial tender mass

Ischiorectal

• 2nd most common
• Larger, indurated, well-circumscribed, located laterally on medial aspect of buttocks

Intersphincteric, deep postanal, pelvirectal

• Rectal pain, skin signs may not be present
• 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

Diagnosis

• CT or US can be useful to define deep abscesses (esp w/ pain out of proportion to exam)

Differential Diagnosis

Anorectal Disorders

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

Treatment

• All perirectal abscesses should be drained in the OR
• 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 w/ packing or cruciate incision w/o packing
  • Frequent sitz baths

Antibiotics

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

Only indicated for:

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

Treatment options:

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

See Also

Anorectal Disorders

External Links

Rob Orman Lecture