Anorectal abscesses include perianal and perirectal abscesses, which are named according to the involved space: ischiorectal, intersphincteric, supralevator, and horseshoe. These are most commonly found in males aged 30 to 50 years old and occur due to occlusion of the mucus-producing anal crypt glands. Patients typically present with severe pain in the perianal area. Constitutional symptoms such as fever and malaise may also be present. Examination will often reveal an area of erythema and perianal fluctuance. Deeper perirectal abscesses may only exhibit tenderness and fluctuance with digital rectal examination. Predisposing conditions include Crohn’s disease, chronic steroid use, diabetes mellitus, malignancy, radiation fibrosis, and trauma.
Perianal Abscess. Swelling and erythema around the anus consistent with a perianal abscess. (Photo contributor: The American Society of Colon and Rectal Surgeons.)
Perirectal Abscess—CT. Hypodense fluid collection surrounded by enhancing ring in the right perirectal tissue suggests an abscess. (Photo contributor: Brett Bechtel, MD.)
Draining Perianal Abscess. A draining, left perianal abscess in a febrile infant. (Photo contributor: Lily Yu, MD.)
Perineal Abscess and Cellulitis. A large perineal abscess is seen extending from the perianal tissues to the right labia in a female infant. (Photo contributor: Lawrence B. Stack, MD.)
Management and Disposition
Incise and drain perianal abscesses using a small cruciate incision lateral to the external sphincter as close to the anal verge as possible. For an uncomplicated abscess, this can be accomplished under local anesthesia. All patients require outpatient follow-up. Antibiotic therapy is advised in immunosuppressed patients and those with systemic symptoms or overlying cellulitis. Commonly used antibiotic regimens are amoxicillin-clavulanate or the combination of ciprofloxacin and metronidazole. Obtain contrast-enhanced computed tomography for suspected deep perirectal abscesses that are not palpable on rectal examination, especially in patients with systemic symptoms. Obtain surgical consultation for large or complicated abscesses or those requiring examination and treatment under anesthesia.
Consider underlying Crohn’s disease in cases of recurrent anorectal abscesses.
All patients warrant surgical follow-up due to the high incidence of fistula formation.
Perirectal Abscess. This large, spontaneously draining perirectal abscess required further surgical debridement in the operating room. (Photo contributor: Lawrence B. Stack, MD.)