Anorectal abscess and fistula
Anorectal abscess and fistula: Excerpt from Professional Guide to Diseases (Eighth Edition)
Anorectal abscess is a localized collection of pus due to inflammation of the soft tissue near the rectum or anus. Inflammation may produce an anal fistula — an abnormal opening in the anal skin — that may communicate with the rectum.
Causes and incidence
The inflammatory process that leads to abscess may begin with an abrasion or tear in the lining of the anal canal, rectum, or perianal skin and subsequent infection by Escherichia coli, staphylococci, or streptococci. Trauma may result from injections for treatment of internal hemorrhoids, enema-tip abrasions, puncture wounds from ingested eggshells or fish bones, or insertion of foreign objects. Other preexisting lesions include infected anal fissure, infections from the anal crypt through the anal gland, ruptured anal hematoma, prolapsed thrombosed internal hemorrhoids, and septic lesions in the pelvis, such as acute appendicitis, acute salpingitis, and diverticulitis. Systemic illnesses that may cause abscesses include ulcerative colitis and Crohn’s disease. However, many abscesses develop without preexisting lesions.
As the abscess produces more pus, a fistula may form in the soft tissue beneath the muscle fibers of the sphincters (especially the external sphincter), usually 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.
The peak incidence of anorectal abscess occurs in people in their 30s and 40s, but there’s also a high occurrence in infants. Men are affected two to three times more often than women. About 30% of patients have a previous history of abscess.
Signs and symptoms
Characteristics are throbbing pain and tenderness at the site of the abscess. A hard, painful lump develops on one side, preventing comfortable sitting. Discharge of pus may occur from the rectum, and there may be constipation or pain associated with bowel movements.
Diagnosis
Anorectal abscess is detectable on physical examination. If the abscess drains by forming a fistula, the pain usually subsides and the major signs become pruritic drainage and subsequent perianal irritation. The external opening of a fistula generally appears as a pink or red, elevated, discharging sinus or ulcer on the skin near the anus. Depending on the infection’s severity, the patient may have chills, fever, nausea, vomiting, and malaise. Digital examination may reveal a palpable indurated tract and a drop or two of pus on palpation. The internal opening may be palpated as a depression or ulcer in the midline anteriorly or at the dentate line posteriorly. Examination with a probe may require an anesthetic. A proctosigmoidoscopy may be performed to exclude associated diseases.
Treatment
Anorectal abscesses require surgical incision under caudal anesthesia to promote drainage. Fistulas require a fistulotomy — removal of the fistula and associated granulation tissue — under caudal anesthesia. If the fistula tract is epithelialized, treatment requires fistulectomy — removal of the fistulous tract — followed by insertion of drains, which remain in place for 48 hours. Warm sitz baths are useful to relieve inflammation; however, pain medication and antibiotics may be needed.
Special considerations
After incision to drain anorectal abscess, follow these guidelines:
❑ Provide adequate medication for pain relief, as ordered.
❑ Examine the wound frequently to assess proper healing, which should progress from the inside out. Healing should be complete in 4 to 5 weeks for perianal fistulas; in 12 to 16 weeks for deeper wounds.
❑ Inform the patient that complete recovery takes time, and offer encouragement.
❑ Stress the importance of perianal cleanliness.
❑ Be alert for the first postoperative bowel movement. The patient may suppress the urge to defecate because of anticipated pain; the resulting constipation increases pressure at the wound site. Such a patient benefits from a stool-softening laxative.
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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Throat abscesses (Professional Guide to Diseases (Eighth Edition))
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