Anal Fistula and Abscess

Perianal or perirectal Abscess

Perianal abscesses are typically polymicrobial with both aerobic and anaerobic bacteria.

-They spread through the external sphincter below the level of the puborectalis and become ischiorectal abscesses.

-Anorectal abscesses are more common in early middle-aged males.

Symptoms & Signs: Severe pain in the anal or rectal area, fever, malaise, purulent rectal discharge ischiorectal abscess:  Swelling in the ischiorectal fossa on digital rectal examination


-Diagnosis can usually be made with physical exam alone;  CT or MRI help to delineate the anatomy of the abscess

Erythema, fluctuance, and swelling in the perianal region on external examination

-Digital rectal exam will reveal a painful swelling laterally in the ischiorectal fossa. Treatment: Perianal abscesses are treated with local incision and drainage, while ischiorectal abscesses require drainage in the operating room.

Prognosis: After drainage of an abscess, most patients are found to have a fistula in ano.

-Delayed treatment can result in tissue necrosis and sepsis.

-Surgical referral after drainage recommended because of the risk of fistula formation.

Anal Fistula

An anorectal fistula is the chronic manifestation of the acute perirectal process that forms an anal abscess

-The majority of anorectal fistulas originate from an infected anal crypt gland

-Drainage of an anorectal abscess results in cure for about 50% of patients while the remaining 50% develop an anal fistula.

-Causes of fistulas that connect to the rectum include: Crohn disease, Lymphogranuloma venereum, rectal tuberculosis, cancer

Symptoms & Signs: purulent discharge, itching, tenderness, and pain

Diagnosis: Drainage from the internal and/or external openings.

-An indurated tract is often palpable.

-Goodsall’s rule can be used as a guide in determining the location of the internal opening

Imaging studies: Endosonography (EUS), fistulography, CT or MRI show air or contrast material within the fistula.

Treatment: Fistula in ano is treated by surgical excision under anesthesia

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