At a glance
An anal fistula is a small abnormal tunnel that connects the inside of the anal canal to an opening in the skin near the anus. It most commonly develops after a perianal abscess. Around half of perianal abscesses are reported to develop into a fistula.
Fistulas can vary in complexity. Some follow a simple, short path. Others take a more winding route through surrounding tissue. The path of the fistula determines which treatment options are most suitable.
This page covers what people commonly experience, how fistulas relate to abscesses, what tends to help, and when to seek care.
How fistulas form
Most anal fistulas begin as an infection in one of the small glands just inside the anus. When this infection forms an abscess and drains — either on its own or through surgery — the tunnel left behind can persist rather than healing shut. That persistent tunnel is the fistula.
Some fistulas are associated with underlying conditions such as Crohn’s disease. Your doctor may want to investigate further if fistulas recur or if you have other symptoms.
Common patterns people report
- Persistent or intermittent drainage of fluid or pus near the anus
- A small opening in the skin near the anus that does not fully heal
- Recurring swelling and pain in the same area, which may improve when drainage occurs
- Discomfort that worsens with sitting, bowel movements, or physical activity
- A cycle of swelling, draining, and temporary relief followed by more swelling
- Irritation or itching around the external opening from ongoing drainage
Diagnosis
Doctors typically diagnose a fistula through a physical examination. They may also use:
- An MRI to map the fistula’s path through the surrounding tissue
- An examination under anaesthesia to evaluate the tract directly
- An endoanal ultrasound in some cases
Understanding the fistula’s path is important because it determines which treatment approach is most appropriate.
Treatment options
Treatment depends on the type and complexity of the fistula. Common approaches include:
- Fistulotomy — the tunnel is laid open and allowed to heal from the inside out. This is common for simpler fistulas.
- Seton placement — a thin thread or loop is placed through the tunnel. It may help drain infection, preserve sphincter muscle, or gradually allow healing.
- Advancement flap — tissue is used to cover the internal opening of the fistula.
- Other techniques — newer approaches continue to evolve. Your surgeon will explain what is most suitable for your situation.
What tends to help
- Keeping the area clean and dry — gentle cleaning after bowel movements and allowing air to the area when possible.
- Sitz baths — warm water soaks can help soothe discomfort and keep the area clean.
- Loose, breathable clothing — avoiding tight clothing that traps moisture against the skin.
- Using a pad or gauze — managing drainage to keep surrounding skin comfortable and dry.
- Following surgical care instructions — attending follow-up appointments and reporting any changes.
What tends to make things worse
- Ignoring persistent drainage or recurring swelling in the same area
- Constipation and straining during bowel movements
- Tight clothing that causes friction and traps moisture
- Delaying follow-up appointments after a drained abscess
- Attempting to squeeze or press on a swollen area yourself
Talking to your doctor
If you are considering seeing a doctor, it can help to note:
- When you first noticed symptoms and how they have changed
- Whether you have had a previous abscess in the area
- The pattern of any drainage — how often, what it looks like
- What you have already tried for comfort
- Whether symptoms come and go or are constant
- Any other health conditions you have been diagnosed with
Many people feel embarrassed discussing these symptoms. Doctors who treat fistulas see them regularly and can help you understand your options.
If you experience severe pain, heavy bleeding, fever, or symptoms that concern you, seek medical care.