Anal abscess

An anal abscess usually forms when an infection in one of the glands around your anus generates pus. The pus gathers in a cavity in the skin and develops into a painful abscess.

The most common type of anal abscess is a perianal abscess, which occurs near your anus and looks like a boil. Anal abscesses can occur in deeper tissue where they are less visible; however, this is less common than superficial anal abscesses.

Men are twice as likely as women to have anal abscesses, which are more common between age 20-60.

An anal abscess needs medical treatment to drain the pus, relieve pain and reduce the risk of further infection. Surgery is usually successful in treating anal abscesses.

Common symptoms of a superficial anal abscess include:

• Anal pain — constant throbbing that usually worsens when you sit down
• Constipation
• Pain when passing a stool
• Redness, swelling and tenderness around your anus
• Unpleasant discharge (pus) or bleeding from your anus

Common symptoms of a deeper anal abscess include:

• Fever — this may be the only symptom you experience if you have a deep anal abscess
• Feeling generally unwell
• Having chills 

If you think you have an anal abscess, see your GP as soon as possible. They’ll ask about your symptoms, and your general health, including any history of bowel conditions.

They’ll examine your anus and rectum to check for pain, redness or swelling, as well as for a visible anal abscess or anal fistula (perianal abscess fistula). About one in two people with an anal abscess develops an anal fistula, a tunnel between your anus and rectum. Sometimes the fistula persistently leaks pus. However, if the opening of the tunnel closes, you may instead have recurring anal abscesses. Surgery is needed to treat anal fistulas.

If there are no visible signs of an anal abscess on the surface of your skin, your GP may use an endoscope (a thin telescope-like tube with a camera on the end) to look inside your anal canal and rectum. If an anal abscess can't be detected by a physical examination, your GP may refer you for an MRI scan or an ultrasound scan. 

Your GP will check for conditions that can cause similar symptoms as an anal abscess. You may therefore be referred for further investigations to check for: 

• Diverticular disease
• Inflammatory bowel disease
• Rectal cancer — this is a rare cause of perianal abscesses
• Sexually transmitted infections (STIs)

Your GP may also refer you to a colorectal surgeon.

The risk of having an anal abscess is higher if you have:

• A weakened immune system, either due to illness, malnutrition or drug abuse
• An STI
• Anal sex — using condoms during sex or anal sex can reduce your risk of anal abscesses
• Certain medical conditions — this includes: 
• Blocked anal glands and/or an anal fissure that becomes infected
• Colitis
• Diabetes
• Diverticulitis
• Inflammatory bowel disease eg Crohn’s disease, ulcerative colitis, other long-term (chronic) bowel conditions
• Pelvic inflammatory disease
• Previously had an anal abscess (up to 50% of abscesses reappear) or an anal fistula 

Certain medical treatments can also increase your risk of anal abscesses, such as: 

• Current or recent chemotherapy
• Medications such as the corticosteroid prednisone

Children and toddlers who have a history of constipation are more likely to have anal fissures, which increases their risk of developing anal abscesses. 

In infants and toddlers, frequent nappy changes can lower their risk of developing anal fistulas and perianal abscesses.

An anal abscess must be surgically drained, as quickly as possible, ideally before it erupts. Your GP or consultant will drain your anal abscess, which can be done under a local or general anaesthetic — deep anal abscesses may need to be drained in a hospital under general anaesthetic while superficial anal abscesses can be drained under local anaesthetic. Drained abscesses do not usually need stitches and are left open to heal. 

Very large anal abscesses may need surgery and in some cases, a catheter (a flexible tube) will be inserted to ensure the abscess drains completely. If you have diabetes or a weakened immune system, you may stay in hospital for several days to check for infection developing. 

Once your abscess is drained, your discomfort and pain should decrease as the pressure of the abscess is relieved. Your anal tissue can then heal. You may still experience some mild pain; your GP or consultant can prescribe you with pain relief and, if necessary, antibiotics.

Your doctor may recommend: 

• Soaking the affected area in warm water three to four times a day
• Stool softeners to make it easier for you to comfortably have a bowel movement
• Wearing a gauze pad or mini pad to soak up any drainage from your abscess

If you have an anal fistula and an anal abscess, surgery to correct both can be performed simultaneously. However, anal fistulas often develop four to six weeks after an abscess is drained, and sometimes several months or years later. Fistula surgery is therefore usually performed separately.

Complications after surgery for an anal abscess include:

• An anal fissure
• Infection
• Scarring
• Your abscess returning

There is currently not much known about how to effectively prevent anal abscesses. However, you can reduce your risk by:

• getting prompt treatment for STIs
• monitoring any health conditions — if you notice problems, see your GP for treatment
• practising good anal hygiene — this is important for both adults and children 
• using condoms — this is especially important during anal sex and reduces your risk of catching an STI during sex or anal sex

Anal abscesses can cause complications but they are treatable.