Anal abscess

What is an anal abscess?

An anal abscess is a painful, pus-filled swelling that develops near your anus, usually when one of the small glands just inside becomes blocked and infected. It's also called a perianal or anorectal abscess.

What are the symptoms of an anal abscess?

The most common symptom is a swollen, red, tender lump near the edge of your anus, a bit like a large boil. Other symptoms can include:

• constant, throbbing pain that's often worse when sitting, coughing or during a bowel movement
• skin that feels warm to the touch
• pus-like discharge from your anus
• constipation or pain when passing a stool
• rectal bleeding
• fever, chills or feeling generally unwell.

Abscesses located deeper inside, rather than just under the skin, may be less visible and less painful at first, but are more likely to cause fever, chills and general tiredness.

What causes an anal abscess, and who's at risk?

About 90% of anal abscesses happen when one of the small glands inside your anus becomes blocked, allowing bacteria or stool to get trapped and infected. Less commonly, an abscess can develop from an infected anal fissure, trauma to the area (including anal sex), a sexually transmitted infection, or an infected cyst.

Certain things increase your risk of developing an anal abscess:

• inflammatory bowel disease, such as Crohn's disease or ulcerative colitis
• diabetes
• a weakened immune system, including from HIV or medicines such as steroids or chemotherapy
• frequent diarrhoea or constipation
• smoking
• pregnancy.

Anal abscesses are more common in men, and most often affect adults between the ages of 20 and 60.

Are there different types of anal abscess?

Most anal abscesses are perianal abscesses, sitting just under the skin near the anal opening; these are the most common and easiest to see and feel. Less commonly, an abscess forms deeper in the surrounding tissue, sometimes called an ischiorectal or supraelevator abscess, depending on exactly where it sits.

Deeper abscesses are less common but are more often linked to inflammatory bowel disease, and tend to cause more general symptoms like fever, rather than an obvious visible lump.

How is an anal abscess diagnosed?

A doctor can usually diagnose an anal abscess from your symptoms and an examination, which includes looking at the area and a digital rectal exam, where a gloved, lubricated finger is used to feel for abnormalities. A speculum may be used to see the area more clearly, and a lighted scope (anoscopy or proctoscopy) can help examine further inside.

If the abscess is deep or the diagnosis isn't clear, an ultrasound, CT or MRI scan may be used. Your doctor may also want to rule out other conditions, such as inflammatory bowel disease or, rarely, rectal cancer.

How is an anal abscess treated?

Once an infection has formed a true abscess, it's unlikely to clear up on its own, and surgical drainage is the main treatment. Never try to drain an abscess yourself, as this risks spreading the infection.

Non-surgical measures

• warm sitz baths (sitting in shallow warm water) several times a day, which can ease pain and swelling
• antibiotics, though these alone are a poor substitute for drainage; they're mainly used alongside surgery for people with a weakened immune system or a more widespread infection
• over-the-counter pain relief.

Surgical drainage

A doctor makes a cut in the skin over the abscess to let the pus drain out. Smaller, superficial abscesses can often be drained in a clinic under local anesthetic, while larger or deeper ones may need a general anesthetic in an operating theatre.

The wound is usually left open rather than stitched closed, since closing the skin too soon can trap infection and cause the abscess to come back. For larger cavities, the wound may be temporarily packed with material to control bleeding, usually removed after 24–48 hours.

Afterwards, you can expect:

• to go home the same day in most cases
• gradually improving pain over 1–2 weeks, managed with over-the-counter painkillers
• regular sitz baths and gentle washing to keep the area clean
• laxatives or stool softeners if needed, to make bowel movements more comfortable
• a return to normal light activity quite quickly, though it's best to wait around a month before strenuous exercise.

Full healing takes around 3 to 4 weeks, and most people return to work within 10 to 14 days, depending on their job and how the wound is healing.

When should you see a doctor?

See a doctor as soon as you notice symptoms of a possible anal abscess, rather than waiting to see if it improves, since untreated infections can spread and become more serious. Don't attempt to drain it yourself.

After treatment, contact your GP or NHS 111 if you develop:

• a fever
• signs the wound is infected, such as worsening pain or pus
• pain that isn't controlled by simple painkillers such as paracetamol or ibuprofen.

Rarely, infection in this area can spread rapidly and become life-threatening (a condition called Fournier's gangrene). Seek emergency care for severe, rapidly worsening pain, swelling or illness.