Background
Perirectal and perianal abscess are commonly encountered ED problems. Timely and appropriate treatment is needed to prevent serious morbidity and mortality.
This article focuses on perirectal abscess and provides some discussion of perianal abscess. These entities are distinct, with potentially different ED evaluation and different treatment and disposition. Differentiation of the more complex perirectal abscess from the more simple perianal abscess is crucial.
Pathophysiology
Perirectal abscess arises from infection of the mucus-secreting anal glands, which drain into the anal crypts. Blockage of the duct is believed to be the initiating cause of infection. The abscess can then progress to involve the potential spaces filled with fatty areolar tissue, which have little resistance to infection. These spaces include the perianal, intersphincteric, ischiorectal, deep postanal space (connecting the ischiorectal space on each side posteriorly), and supralevator spaces. These spaces may become infected alone or in combination with one another.
Perirectal abscess is usually an aerobic and anaerobic polymicrobial infection. Bacteroides fragilis is the predominant anaerobe. Other common bacteria include Escherichia coli and those of the genera Proteus, Bacteroides, and Streptococcus. Sources of bacteria are skin, bowel, and, rarely, the vagina.1
A variety of disease states is associated with the development of an abscess; these include Crohn disease, carcinoma, radiation fibrosis, trauma, Hodgkin disease, and immunocompromised states. Associated infectious causes include Chlamydia, Actinomyces, Gonococcus, Streptococcus, Bacteroides, and Proteus species; Staphylococcus aureus and Escherichia coli; and herpes, tuberculosis, and lymphogranuloma venereum.
In contradistinction to perirectal abscess, perianal abscess is easily palpable and is not accompanied by fever, leukocytosis, and sepsis in the immunocompetent patient.
Mortality/Morbidity
In rare instances, inappropriately treated perirectal abscess may result in death.
Perirectal abscess results in fistula formation in 25-50% of cases.
Bacteremia and sepsis may result, especially in immunocompromised patients.
In infants, fistula formation ensues after drainage of an abscess in 35% of cases.
Urinary retention (often resulting in lengthened hospitalization) occurs in 5% of cases.
Fournier gangrene has occasionally been reported.
Race
No racial predilection has been found.
Sex
Men are affected more frequently than women, with a male-to-female predominance of 2:1 to 3:1.
Age
Perirectal abscess occurs in all age groups, from infants to elderly persons. The peak incidence is in the third and fourth decades of life
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