Perianal abscess

What is a perianal abscess?

It is a cavity with infected fluid around the anus consisting of bacteria and dead tissue. It can develop superficially and be visible against the skin around the anus, but sometimes it’s not apparent if the abcess spreads deeper in the tissues.

• 90% of abscesses form by obstructing and infecting glands (cryptoglobular) in the anal sphincter. These are the same glands that dog sniff on each others anus. The infection can spread from the anal canal to tissue around the anal canal, this can be on the skin or deeper in the fatty tissue.

• Perforation of an anal or rectal cancer
• Digital anal lesions

• Perforation by a foreign object (sexual practice, fish bones, etc.)
• Perforation in inflammatory bowel disease, tuberculosis or actinomycosis

– Frequency: 16.1 / 100000 persons

– Men > women (men 2x more frequent than women)

– Average age 40 years

– Smoking

– Inflammatory bowel disease

– HIV infection

There is no increase if there is a lack of personal hygiene or a sedentary lifestyle.

A combination of one or more of the following symptoms:

– Painful swelling

– Redness

– Fever

– Foul smelling fluid loss if the abscess spontaneously breaks open.

Incision and drainage

• During surgery usually under general anesthesia, the infection is controlled by incising the abscess to drain the pus from the abscess cavity. After rinsing the cavity with a fluid (water,  Povidone-iodine  liquid), the wound is filled with a small gauze wick.

See surgical procedure: Incision and drainage –  Perianal abcess

• The first postoperative day, the gauze wick is removed.
• Depending on the surgeon’s preference, it may be necessary for a home nurse to apply daily a gauze wick in the abscess cavity.

It is important to help the infected fluid to drain from the wound. The skin should not close before the cavity is closed, otherwise another abscess can develop.

If a daily gauze wick is not applied, the wound edges should be opened daily by applying traction to the opposite edges of the wound.

Smith SR, Newton K, Smith JA, et al. Internal dressings for healing perianal abscess cavities. Cochrane Database Syst Rev 2016;(8):CD011193.pmid:27562822.

Antibiotics are not routinely prescribed after incision and drainage of an abscess.

Antibiotics are prescribed in case of :

– Severe cellulitis

– Diabetes

– Compromised immune system (corticosteroids, transplantation, dialysis)

When an abscess is still too small to be incised, antibiotics can be used to treat the infection.

An anal fistula develops in 40-50% of patients after incision and drainage of an anal abscess.

An anal fistula occurs when the internal opening in the anal canal remains open. Fecal fluid that enters through an internal opening in the anal canal slowly continues to seep into the abscess cavity and prevents the complete closure and healing of the abscess cavity.