Epidemiology and Etiology
- Approximately 100,000 new cases per year in the United States
- Usually presents between 20 and 60 years of age
- Mean: 40 years
- Twice as common in men as in women
- 30% of patients report a prior history of anorectal abscess.
Infection of an obstructed glandular crypt may occur due to:
- Nonspecific obstruction (approximately 90% of cases)
- Inflammatory bowel disease (especially Crohn disease)
- Extension of another infection:
- Pelvic inflammatory disease
- Escherichia coli
- Staphylococcus aureus
- Rectal prolapse
Classification and Pathophysiology
The classification of anorectal abscesses is based on their location.
- Perianal abscess (most common)
- Obstruction of an anal crypt gland allows bacterial growth → abscess
- The abscess can spread along planes to:
- Intersphincteric, ischiorectal, or supralevator spaces → perirectal abscess
- Perianal skin → perianal abscess
Clinical Presentation and Diagnosis
The symptoms of a perirectal or perianal abscess can vary based on its location, but may include:
- Anal or rectal symptoms:
- Dull, sharp, aching, or throbbing
- May be exacerbated by bowel movements or sitting
- Constipation or diarrhea
- Purulent drainage
- Rectal bleeding
- Constitutional symptoms:
- Fever (21%)
- Perianal swelling and erythema may be seen.
- Depending on the location, external or digital rectal exam may reveal:
- Spontaneous drainage may be bloody or purulent.
The diagnosis of a perirectal or perianal abscess is made clinically. However, CT, MRI, or ultrasonography may be useful for identifying:
- A deep abscess
- A potential intra-abdominal source of infection
Management and Complications
- Standard of care
- All anorectal abscesses should be drained promptly.
- A simple, perianal abscess can be drained in an office or ED.
- Complex perirectal abscesses require drainage in an OR.
- Ciprofloxacin plus metronidazole
- Extensive cellulitis
- Signs of sepsis
- Valvular heart disease
- Keep incision site clean.
- Stool softeners
- Sitz baths
- Recurrent abscess
- Fistula formation
- Urinary retention
- Constipation or incontinence
- Fournier gangrene:
- Necrotizing fasciitis of the external genitalia, perineal, or perianal area
- Associated with a high rate of mortality
- Anal fissure: a superficial tear in the anoderm associated with constipation, trauma or inflammatory bowel disease: Patients present with rectal pain during bowel movements, passage of bright red blood, and anal spasm. The diagnosis is clinical. Management is usually conservative and includes increasing fluid and fiber intake, warm sitz baths, and stool softeners. Topical nifedipine helps with anal spasms, and local anesthetics provide pain control.
- Anal fistula: abnormal communications between the anorectal lumen and another body structure, often to the skin: Anal fistula can occur because of extension of an anal abscess. Symptoms include pain and abnormal discharge. The diagnosis is clinical. Management is primarily surgical (fistulotomy) but can include antibiotics if infection is present.
- Hemorrhoids: dilated vessels of the hemorrhoidal plexus in the anal canal, commonly caused by constipation: Depending on the location of the veins, hemorrhoids can be internal or external. External hemorrhoids are painful, whereas internal hemorrhoids are painless. Both types can bleed and appear as a soft rectal mass on exam. The diagnosis is clinical. Management includes stool softeners, topical hydrocortisone, and sitz baths. Additional treatment options are rubber band ligation or surgical removal.
- Pilonidal cyst: can present as an abscess: Like perianal abscesses, pilonidal cysts present with erythema, tenderness, and swelling. However, pilonidal abscesses occur in the intergluteal area superior and dorsal to the anus. These cysts are diagnosed by physical examination and are treated by surgical incision and drainage.
- Anal carcinoma: neoplastic disease in which cancer cells form and grow in the anus: Risk factors include older age, infections such as HPV, multiple sexual partners, and anal sex. Symptoms include bleeding from the anus, anal pain, anal mass, or itching. Anal carcinoma is diagnosed by biopsy. Management can include surgery, radiation, or chemotherapy.
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- Sigmon DF, Emmanuel B, Tuma F. (2020). Perianal abscess. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK459167/
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- Whiteford MH (2007). Perianal abscess/fistula disease. Clinics in Colon and Rectal Surgery 20(2):102–109. https://doi.org/10.1055/s-2007-977488
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