Medical Clinic

Anorectal Abscess and Fistula

Anorectal abscess is a localized infection that appears as a collection of pus due to inflammation of the soft tissue. As the abscess produces more pus, a fistula can form, creating an abnormal opening in the anal skin.

A fistula usually forms in the soft tissue beneath the muscle fibers of the sphincters (especially the external sphincter), extending into the perianal skin. The internal (primary) opening of the abscess or fistula is usually near the anal glands and crypts; the external (secondary) opening, in the perianal skin. In severe cases, this opening may communicate with the rectum.


An abscess results when a small gland just inside the anus becomes infected from bacteria or stool trapped in the gland. You did nothing to cause this infection. Certain conditions--constipation, diarrhea, colitis, or other inflammation of the intestine, for example--can sometimes make these infections more likely.

Signs and Symptoms

Signs and symptoms depend on the infection's severity and whether or not the abscess is a chronic condition. Assessment findings also vary according to the type of abscess.

Usually, the first symptom the patient reports is rectal pain, which he usually describes as throbbing. Occasionally, diarrhea precedes the onset of rectal pain. The patient may state that he can't sit comfortably because of the development of a hard, painful lump on one side.

If the anorectal abscess is a chronic condition, the patient may report discharge or bleeding and anal pruritus. If he also has an anal fistula, anal pruritus and purulent discharge are commonly reported.

Depending on the severity of the infection, the patient may also complain of fever, chills, nausea, vomiting, and malaise.

Inspection may reveal an erythematous lump or swelling in the anal area. If the patient has a fistula, its external opening may be visible as a pink or red, elevated, discharging sinus or ulcer on the skin near the anus. Palpation usually reveals tenderness over me reddened or swollen area.

Digital examination of the patient with a fistula may disclose a palpable, indurated tract and a depression or ulcer in the midline anteriorly or at the dentate line posteriorly.

Diagnostic tests

Sigmoidoscopy, barium enema, and colonoscopy may be performed to rule out other conditions.


Anorectal abscesses require surgical incision and drainage, usually under caudal anesthesia. Fistulas require fistulotomy (removal of the fistula and associated granulation tissue) under caudal anesthesia. If the fistula tract is epithelialized, treatment requires festulectomy (removal of the fistulous tract) followed by insertion of drains, which remain in place for 48 hours. Fistulas that result from an intestinal disorder, such as Crohn's disease, are usually treated conservatively because surgery is often not successful.

  • Follow regular bowel habits without any strain
  • Treat any infections or boils immediately
  • Avoid nylon underwear and use cotton ones
  • Follow hygeinic measures to keep anal area clean and dry

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