saudigastro.com/patients/anal-fistula-abscess
Category
Common
Red flags
5
This article is educational and does not replace your doctor's advice. Seek urgent care for any red-flag symptoms.
What is it?
Close to the anus there are small glands that make mucus. If one of these glands becomes blocked and infected, pus collects and forms an abscess (a painful, swollen pocket of infection). After the abscess is drained or bursts, a fistula can remain: a small abnormal tunnel connecting the inside of the anal canal to an opening in the skin near the anus. A fistula may drain pus or blood from time to time. The two are really stages of the same problem.
How common is it?
Anal abscesses are fairly common, especially in adults and more often in men. A fistula develops in a considerable share of people after an abscess. People with Crohn's disease are more likely to have fistulas, and these can be more complex.
Why does it happen?
Most often a blocked anal gland becomes infected by the normal bacteria of the bowel. Less commonly the cause is Crohn's disease, a previous injury or surgery, radiation, tuberculosis, or other infections. Diabetes and conditions that weaken the immune system can make the infection more serious. It is not caused by poor hygiene or by something you did wrong.
Symptoms
- Constant, throbbing pain near the anus that is worse when sitting, walking or passing stool
- A red, hot, swollen, tender lump beside the anus
- Fever, chills and feeling unwell with an abscess
- Pus, blood or foul-smelling discharge from a small opening in the skin near the anus (fistula)
- Skin irritation and itching around the anus from the discharge
- Pain that eases for a while after the abscess drains, then returns
- Difficulty or pain with bowel movements
Red flags — seek urgent medical care
Severe anal or buttock pain with fever or chills
This suggests an abscess that needs draining. See a doctor the same day or go to the emergency department.
Redness, swelling and pain spreading over the buttock, groin or genitals, or skin that looks dark or blistered
Rarely, the infection spreads quickly into deeper tissue and becomes life-threatening. Go to the emergency department immediately.
Fever, fast heartbeat, confusion or feeling faint
May mean the infection has reached the blood. This is an emergency: call emergency services.
Difficulty passing urine together with severe anal pain
A deep abscess may be pressing on nearby structures. Seek urgent care.
Diabetes or a weakened immune system with any anal swelling or pain
Infections can worsen faster in these conditions, so be seen early without waiting.
How is it diagnosed?
Your doctor will look at and gently examine the area. An abscess is often recognised by the examination alone. To find the fistula tunnel and how it relates to the muscles that control the bowel (the sphincter), you may need an MRI of the pelvis, an ultrasound done through the anal canal, or an examination under anaesthesia by a colorectal surgeon. If Crohn's disease is suspected, a colonoscopy and other tests may be arranged. The doctor decides which tests you need.
What the latest science says
The main treatment of an abscess is drainage; antibiotics alone are not enough for most people, and are added only in selected situations. For fistulas, surgeons choose from several techniques that aim to close the tunnel while protecting the muscles that keep you continent. Treatment of fistulas in Crohn's disease often combines medicines with surgery.
Outlook — what to expect
After drainage, many people heal without further problems, but a fistula can remain or return, and it often needs a planned operation. Fistulas can usually be treated successfully, though some need more than one procedure. Surgery near the sphincter carries a small risk of changes in bowel control, which your surgeon will discuss with you.
Treatment
Habits & Lifestyle
An abscess is not something to treat at home. Simple measures help comfort and healing after a doctor has treated it.
- See a doctor promptly for any painful anal swelling; do not try to squeeze, pierce or cut it yourself
- Warm sitz baths (sitting in a few centimetres of warm water) can ease pain and keep the area clean after treatment
- Gently clean after bowel movements and pat dry; avoid harsh soaps and rubbing
- Use a pad or gauze if there is drainage, and change it when damp
- Follow wound-care and follow-up instructions, and tell the team if the pain or discharge returns
Diet
No special diet cures a fistula, but keeping stools soft avoids straining and pain.
- Eat fibre-rich foods such as vegetables, fruit, whole grains and legumes
- Drink enough fluids through the day
- Do not sit on the toilet for long periods or strain
- If you have diabetes, keep your sugar well controlled, as it helps healing
Medications
Medicines support treatment but do not replace drainage or surgery. Your doctor decides which, if any, you need.
- Simple pain relief as advised by your doctor
- Antibiotics only in selected situations, such as spreading infection, diabetes or a weak immune system
- Stool softeners or fibre supplements if constipation causes pain or straining
- For fistulas linked to Crohn's disease, specific bowel-disease medicines may be used by the specialist
Procedures & Surgery
Drainage of the abscess and, for a persistent fistula, a planned operation are the core of treatment.
- Incision and drainage of the abscess, often under local or general anaesthesia
- Fistulotomy (laying open the tunnel) for simple fistulas that do not involve much sphincter muscle
- A seton, a soft thread placed through the tunnel to keep it draining and prevent new abscesses
- Sphincter-sparing techniques such as flaps, plugs or glue for more complex fistulas
- Your surgeon will explain the risks, including recurrence and a small risk to bowel control
Living with the condition
- Healing can take weeks; keep follow-up appointments even when you feel better
- A persistent fistula is common and treatable; discuss options with a colorectal surgeon
- If you have Crohn's disease, keep your bowel disease well controlled
Questions to ask your doctor
Save this list or print it before your appointment — doctors appreciate prepared patients.
- Do I have an abscess, a fistula, or both?
- Do I need an MRI or an examination under anaesthesia?
- Could this be related to Crohn's disease or another condition?
- Which operation do you recommend and what is the risk to my bowel control?
- How long will healing take and what care do I need at home?
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Status: Approved for publication by SGA; individual clinician review is ongoing · Published 24/04/2026
For general education only; it does not replace your doctor’s advice. Individual clinician review of this guide is ongoing. SGA clinician? Review this guide