Anal Fistula: What You Need to Know (2025)

What Is an Anal Fistula?

An anal fistula is an abnormal tunnel that forms between the inside of theanus (the hole at the end of your digestive tract through which solid waste leaves the body) and the skin around it. It usually forms after an infection in one of the glands inside the anus, which causes a painful collection of pus, or abscess. If the abscess doesn’t heal properly, it may drain where it shouldn’t, leaving behind a fistula.

Your doctor can repair the fistula, but you'll likely need a small surgery.

Anal Fistula Types

The location and path of the fistula will determine which kind you have. The main types include:

Intersphincteric anal fistula. Inside your rectum, two ring-like muscles control the opening and closing of your anus, called the internal and external sphincters. If you have an intersphincteric fistula, the tunnel forms between the internal sphincter and the skin around your anus. This is the most common type of fistula.

Transspincteric anal fistula. This type forms a longer tunnel that passes through both the internal and external sphincter muscles.

Suprasphincteric anal fistula. This type of fistula travels up and over the internal sphincter before exiting through the skin on the other side.

Extrasphincteric fistula. This is the most uncommon type of fistula. It starts higher up in the rectum and extends around both the internal and external sphincter muscles.

Superficial anal fistula. Unlike the other types of fistulas, this type starts inside the anus but travels around the sphincter muscles, then curves back down and exits through the skin.

Anal Fistula Causes

Just inside your anus are several glands that make fluid. Sometimes, they get blocked or clogged. When that happens, bacteria can build up, creating a swollen pocket of infected tissue and liquid. Doctors call this anabscess.

If you don’t treat the abscess, it can grow and create a hole in theskinsomewhere near your anus so the pus inside it can drain. A fistula is the tunnel that forms, connecting the infected gland to the opening of the skin.

Anal Fistula Risk Factors

Most of the time, an abscess causes a fistula. It’s rare, but some conditions may also cause them, including:

  • Tuberculosis
  • Sexually transmitted diseases
  • Inflammatory bowel diseases, such as Crohn’s diseaseorulcerative colitis
  • Actinomyces bacterial infections
  • Anal cancer treatments
  • Having an anal abscess drained in the past
  • Injury to the area around the anus
  • An infection in the area around the anus

Anal Fistula Symptoms

The most common symptoms are:

  • Pain
  • Redness
  • Swelling around your anus

You might also notice:

  • Bleeding
  • Painful bowel movements or urination
  • Fever
  • A foul-smelling liquid oozing from a hole near your anus

If you have any of these symptoms, you should speak with your doctor.

Anal Fistula Diagnosis

If your doctor thinks you have an anal fistula, they'll ask about your medical history and give you aphysical exam.

Some fistulas are easy to spot; others aren’t. Sometimes they close on their own, then open back up. Your doctor will look for signs of oozing fluid or bleeding. The doctor might also gently put a finger into your anus during the exam to feel for lumps or swelling.

The doctor may send you to a specialist incolonand rectal conditions for more exams or imaging tests, such as X-rays or aCT scan. In some cases, you might need a colonoscopy, where the doctor will put a tube with a camera on the end into your rectum to look at the inside of your bowels. You’ll be asleep when this happens.

Anal Fistula Treatment

The exact type of treatment you receive will depend on the location, size, and type of fistula. Most anal fistulas need surgery to fix them. Treatment options include:

Fistulotomy

This is done in the case of a simple fistula that doesn’t pass through much muscle. For this, your doctor will make an incision along the length of the tunnel to open it up anddrain any pus, then flatten it and stitch it into place to heal. Because most of the muscle is left intact, the risk of incontinence (losing control of your bowels) is generally low. If the sphincter muscles do need to be cut, it might be harder to control your bowels afterward. This is an outpatient treatment, so you’ll be able to go home the same day.

Fistulectomy

During a fistulectomy, the surgeon cuts out the entire fistula. This approach can be used for more complicated or recurring fistulas, but since there’s a higher chance of damaging your sphincter muscles, your doctor may try other treatments first.

Seton placement

For a more complicated fistula — one that passes through a lot of the sphincter muscles or has branches — your doctor might loop a surgical thread, called a seton, through the fistula. The seton keeps the fistula open, helping drain the infected fluid. It can also slowly cut through the fistula tract as it moves through your muscle, allowing the area to heal. The seton may be left in for a few weeks. This is a nonsurgical procedure, but it can be combined with surgery.

Mucosal advancement flap

Fistulas that pass through your sphincter muscles can also be fixed with a mucosal advancement flap. During this procedure, your surgeon will create a flap of healthy tissue from inside the rectum, and then use it to cover the internal opening of the fistula. This blocks the fistula from inside while still allowing it to drain from the outside, helping it heal naturally.

Fistula plugs

Fistula plugs are a newer, less invasive way to treat anal fistulas. These small plugs — usually made from materials such as collagen to encourage tissue growth — are placed inside the fistula to block the tunnel and encourage healing. Over time, the body absorbs the plug and the fistula closes. While fistula plugs are still not as common as traditional surgery, they can be a good choice for simpler fistulas.

Ligation of intersphincteric fistula tract (LIFT)

This surgery is used to treat more complicated fistulas, especially those that pass through the anal sphincter muscles. During the LIFT procedure, the surgeon makes a small cut to access the fistula tract, then closes the tunnel between the muscle with stitches. They may also remove the fistula tract or clean out any infection. This procedure is usually done in combination with a seton drain. While it might not be as effective as a fistulotomy, the LIFT has the benefit of preserving the sphincter muscles.

Anal Fistula Complications

An anal fistula won’t go away on its own. If left untreated, it could lead to complications, including:

Recurrent infections

If a fistula is left untreated, it can continue to collect bacteria and pus, leading to repeat infections. These may get worse over time, causing discomfort and potentially making it harder to treat.

Fecal incontinence

If the fistula affects or damages your sphincter muscles,you may have a harder time controlling your bowel movements. While rare, some people who have surgery to repair an anal fistula may also face this problem.

Severe infections

If the infection in the fistula spreads into nearby tissue or the bloodstream, it can cause more serious problems such as sepsis (a life-threatening response to an infection). This requires urgent medical treatment.

New extensions of fistulas

Untreated fistulas can branch out and form new tunnels, creating more fistulas that connect to different areas of the skin around the anus. These are harder to fix.

Anal fistula cancer

Though rare, anal fistulas that go untreated for a long time can raise your chances of developing anal cancer. Ongoing inflammation and repeated infections could lead to changes in the tissues, which might cause cancerous growths in some cases.

Anal Fistula Prevention

While you can’t usually prevent an anal fistula, there are things you can do to lower your chances of developing another condition, such as Crohn’s disease, which can lead to fistulas. Maintaining a healthy lifestyle by exercising regularly and eating enough fruits and vegetables can help.

Takeaways

An anal fistula is a tunnel that forms between the inside of the anus and the skin around it, often causing pain, swelling, and bleeding. It won’t heal on its own and usually needs surgery to fix. If left untreated, anal fistulas can lead to complications such as repeated infections, new fistulas, or even cancer in rare cases. If you think you have an anal fistula, talk to your doctor about which treatment option is best for you.

Anal Fistula FAQs

What is the main cause of a fistula?

Most fistulas happen when an untreated abscess causes an infection in the anal glands, forming a tunnel between the inside of the anus and the skin to allow the infection to drain.

How do you know if you have a fistula?

The symptoms of a fistula include pain, swelling, redness near the anus, and leakage of blood or a foul-smelling fluid. A doctor can check whether you have a fistula with a physical exam.

Is a fistula serious?

If a fistula isn’t treated, it can become serious, causing problems such as recurrent infections, new fistulas, or in rare cases, even cancer.

How to cure anal fistula

Most fistulas need surgery to fix, but there are some newer nonsurgical options available.

What is the recovery time from perianal fistula surgery?

Your recovery time will depend on the type of fistula you have, but most people heal from surgery within 3-6 weeks.

Anal Fistula: What You Need to Know (2025)
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