CHAPTER 25: ANORECTAL ABSCESS

CASE SCENARIO

A 45-year-old man with a past medical history of hypertension presents to the emergency room with a 2-day history of rectal fullness and perirectal pain. The pain is throbbing in nature and mildly worsens with a bowel movement.

The patient is afebrile, with blood pressure elevated to 150/95. On examination, his abdomen is non-tender. Rectal examination reveals an exquisitely painful mass in the left lateral position. A full rectal examination is impossible due to the pain. His lab work is unremarkable with the exception of a leukocytosis to 15.

EPIDEMIOLOGY

Although failure of patients to seek medical attention and misattribution of anorectal pain to hemorrhoids confound epidemiological data, an estimated 100,000 cases of anorectal abscess are diagnosed yearly in the United States.¹ Most patients present between the ages of 20 to 60, with a mean age of 40 in both genders.² In adult patients, males are twice as likely to develop an abscess compared to women. Interestingly, neither personal hygiene nor sedentary occupation has been linked to development of an anorectal abscess.

PATHOPHYSIOLOGY

Anorectal abscesses originate from an infection of the anal crypt gland. When the gland becomes obstructed, suppuration follows the path of least resistance into the wall of the anal canal. Knowledge of anatomy is essential in knowing the five possible tracts (Figure 25–1):

1. Intersphincteric abscess—the infection extends between the internal and external sphincter, sparing the anal verge.

2. Perianal abscess—the infection extends between the internal and external sphincter to reach the anal verge.

3. Ischiorectal abscess—the infection ruptures through the external sphincter into the ischiorectal fat.

4. Supralevator abscess—the infection extends above the levators.

5. Horseshoe abscess—the infection starts in the deep postanal space and then extends to either or both ischiorectal fossae.

In terms of natural history of the disease, there are the three possible outcomes. An abscess can

1. drain and heal

2. drain and form a fistula

3. remain undrained and progress to anal sepsis, with high morbidity and mortality

CLINICAL PRESENTATION

The primary presenting symptom of an anorectal abscess is pain in the anal or rectal area. The pain is constant and is not necessarily associated with bowel movements. Systemic symptoms such as fever and malaise are common. With spontaneous opening, purulent rectal drainage may be seen.

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