Digestive health centre

Anal abscess, perianal abscess and anorectal abscess

An anal abscess is a painful condition in which a collection of pus develops near the anus. Most anal abscesses are a result of infection from small anal glands.

An anal abscess can often lead to another painful condition, an anal fistula - a small channel that can develop between the end of the bowel and the skin near the anus.

The most common type of abscess is a perianal abscess. This often appears as a painful boil-like swelling near the anus. It may be red in colour and warm to the touch. Anal abscesses located in deeper tissue are less common and may be less visible.

Another type of abscess is an anorectal abscess, which occurs when pus builds up in both the rectum and anus. The rectum is the area of the large intestine where stools (faeces) are stored. This type of abscess can be caused by a sexually transmitted infection (STI), a blocked gland or the infection of an anal fissure.

Antibiotics and surgical incision and drainage is the most common treatment for all types of anal abscesses and is usually successful.

After an abscess has been drained, however, about 40% of patients will develop a complication called a fistula. A fistula is a small channel that makes an abnormal connection between the site of the abscess and the skin.

In some cases, an anal fistula causes persistent drainage. In other cases, where the outside of the channel opening closes, the result may be recurrent anal abscesses. The only cure for an anal fistula is surgery.

Causes of anal abscesses

An anal abscess can have many different causes. These include:

• Infection of an anal fissure. An anal fissure is a small superficial tear in the skin of the anal canal.
• A growth or ulcer (painful sore).
• A complication from surgery.
• A congenital abnormality (a health issue you are born with).
• Sexually transmitted infections.
• Blocked anal glands.

Risk factors for anal abscesses include:

• Inflammatory bowel syndrome (IBS)
• Ulcerative colitis
• Crohn’s disease
• Diabetes
• Diverticulitis
• Pelvic inflammatory disease
• Being the receptive partner in anal sex
• Cancer of the rectum
• Tuberculosis (TB)
• Chlamydia
• Syphilis

For adults, using condoms during sexual intercourse, including anal intercourse, can help prevent anal abscesses. For infants and toddlers, frequent nappy changes and proper cleaning during nappy changes can help prevent anal fissures and perianal abscesses.

Treatment

Anal abscesses are usually treated with antibiotics and a procedure to drain infected fluid away from the abscess.

After an anal abscess has properly healed, it's unlikely that the problem will come back. To prevent one from doing so, however, it's important to follow the advice of your doctor or bowel and rectal surgeon.