What Is an Anal Fistula?
Published on March 7, 2025
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An anal fistula is a tunnel that develops from the inside of the anus to the skin outside. It usually starts near blocked or infected anal glands and forms an abscess (a pus-filled pocket). Pus and fluid collect in this space, which then tunnels to the outside, where it drains.
From the outside, an anal fistula (also called a fistula-in-ano) looks like a small hole in the skin close to your anus. You may notice pus, blood, or stool draining from it. The most common symptoms of an anal fistula are anal pain, swelling, redness, and fluid drainage from the opening. Treatment options vary, but most anal fistulas require surgery.
Types of Anal Fistulas
Healthcare providers categorize anal fistulas based on their location. Each type relates to its proximity to your anal sphincter muscles, which control your bowel movements.
- Intersphincteric anal fistula: A fistula that forms in the internal anal sphincter muscle, then leads out between the internal and external sphincter muscles.
- Transsphincteric fistula: A fistula that forms in both layers of anal sphincter muscles.
- Suprasphincteric fistula: A fistula that forms in the internal sphincter, then leads around the external sphincter.
- Extrasphincteric fistula: A less-common fistula that forms around both sphincter muscles.
- Superficial anal fistula: A fistula that bypasses all muscles.
Extrasphincteric fistulas and superficial anal fistulas don't come from blocked anal glands but are still called anal fistulas based on their location.
Signs and Symptoms of an Anal Fistula
One of the most common symptoms of an anal fistula is pain in and around the anus. Swelling and inflammation associated with an anal fistula can cause intense discomfort. The pain usually gets worse when you apply pressure to the area by sitting, coughing, or pooping.
Besides anal pain, symptoms of an anal fistula include:
- Fluid drainage (including pus, blood, or stool) from the fistula
- A visible opening on the skin near the anus
- Redness, inflammation, and itching around the opening
- Fever and chills
- Fatigue
- Feeling generally sick
- Pain with urination
- Trouble holding stool in
Fistula symptoms may ease temporarily but tend to come back in the same area every few weeks.
Causes and Risk Factors of Anal Fistulas
Most types of anal fistulas are caused by a perianal abscess (the blockage, inflammation, and infection of the anal glands). These small glands sit inside your body near the anal opening and typically cause no trouble. But certain medical conditions and risk factors can make them more likely to get clogged and infected.
Risk factors for anal fistulas include:
- Being male
- Having a current or prior history of perianal abscesses
- Having an inflammatory bowel disease (IBD) like Crohn's disease
- Having had surgery in the anal region
- Having had radiation treatment for rectal cancer
- Experiencing a traumatic injury
- Having an infection in the anal area
- Having chronic sexually transmitted infections
- Having tuberculosis
- Having hidradenitis suppurativa
- Having obesity
- Having diabetes
- Having high cholesterol
How Is an Anal Fistula Diagnosed?
Anal fistulas are diagnosed by a gastrointestinal specialist (gastroenterologist) or a colorectal surgeon. They'll perform a physical examination, ask about your medical history and symptoms, and order diagnostic tests.
Common tests used to diagnose an anal fistula include:
- Anoscope, a small tube with a light and camera that helps see the anal canal.
- Magnetic resonance imaging (MRI), an imaging scan that produces detailed images of the fistula and sphincter muscles.
- Fistulography, which involves a contrast injection (dye) to show the path of the fistula on an X-ray.
- Fistula probe, a tool that's inserted into the fistula to map its tunnel.
It may be difficult to find the fistula opening inside the anus. Sometimes, providers inject hydrogen peroxide into the outer opening to help locate the infection at the source of the fistula. The hydrogen peroxide will form bubbles or foam at the site of the infection.
For persistent and very painful anal fistulas, your provider may recommend diagnostic surgery to examine it and identify any potential complications. If your provider suspects you may have an IBD like Crohn's disease, they may order a colonoscopy to diagnose this related condition.
Treatment and Medication Options for Anal Fistulas
In most cases, treating an anal fistula involves surgery. But if your fistula is caused by Crohn's disease and isn't infected, it may heal with medical treatment for Crohn's. Sometimes, both medicine and surgery are used for fistulas among people with Crohn's. All treatment options aim to repair the fistula while protecting the important sphincter muscles nearby.
Medication Options
As mentioned, if you have an IBD like Crohn's disease, the medications used to treat it may help resolve your fistula if it's not infected. Your provider may also prescribe antibiotics to be used alongside surgery in some cases, but these drugs will not repair a fistula on their own.
Surgery
Since medication alone typically cannot heal an anal fistula, surgery is the most common treatment. Surgical options to treat anal fistula include:
- Fistulotomy This surgery opens the fistula further so it can heal from the inside out.
- Glue and plug A newer treatment option, this procedure closes the inner fistula opening. Then, your provider fills the tunnel with a special type of glue and seals the outer opening with a collagen plug.
- Seton placement During this procedure, the surgeon places a suture or rubber band (seton) inside the fistula, which keeps it open and allows it to drain and heal from the inside out.
- Endorectal advancement flap (ERF) In this procedure, a surgeon removes the fistula's internal opening, then covers it with a flap removed from the rectal wall. This procedure preserves more sphincter muscle than other options.
- Ligation of the intersphincteric fistula tract (LIFT) A two-stage treatment, the LIFT procedure works best for deep or complex fistulas. A surgeon places a seton into the tunnel, which gradually helps widen it. Then, weeks later, the surgeon removes any infected tissue and closes the internal tunnel opening.
- Muscle flap Also for complex fistulas, this procedure fills the tunnel with healthy muscle removed from the thigh, buttocks, or labia.
- Ostomy and stoma For persistent fistulas that haven't healed with other methods, your provider may recommend bypassing your anus altogether until the fistula can fully heal. This is done via a procedure called an ostomy. This involves creating a temporary opening (called a stoma) in your abdomen to temporarily divert your intestines away from your anal canal. After surgery, you'll wear an ostomy pouch over the stoma to collect waste. This process can be reversed once the fistula has healed.
Prevention of Anal Fistula
To prevent an anal fistula, you must first prevent anal abscesses from forming around your anal glands. Lifestyle changes that can help prevent anal fistulas include:
- Healthy dietary habits with an adequate fiber intake
- Daily exercise
- Safe sex practices
- Regular cleaning of the area around your anus, including through daily showering or washing the area when soiled
If you have any symptoms of an IBD, like weight loss, abdominal pain, blood in your stool, or chronic diarrhea, let your healthcare provider know right away. Early diagnosis and treatment of Crohn's disease or other IBDs can help reduce risk of anal fistulas.
Lifestyle Changes for Anal Fistulas
After surgery for an anal fistula, these lifestyle and self-care strategies can help your body recover:
- Soak in a warm bath three to four times a day.
- Wear a pad over your anal area during healing.
- Increase fiber in your diet.
- Drink plenty of fluids to prevent constipation.
- Use a provider-approved stool softener.
- Avoid straining during a bowel movement.
- Wait until your surgeon clears you to resume your usual activities.
How Long Do Anal Fistulas Last?
The prognosis of an anal fistula depends on how simple or complex it is. It typically takes three to six weeks to heal from one or more surgeries. Recovery from more extensive surgeries may take up to 12 weeks.
Once an abscess or fistula exists, it can come back even after treatment. The symptoms of an anal fistula left untreated may come and go every few weeks, but most anal fistulas recur without surgery.
Complications of Anal Fistula
The most common complication of an anal fistula is recurrence, meaning it comes back after healing.
Other potential complications include:
- Inability to hold in stool (fecal incontinence)
- Chronic infection
- Fistula extension to new areas
- Anal cancer
- Chronic draining of fluids at the opening
- Anal stricture (a narrowing of the anal canal which can make it difficult to pass stool)
Research and Statistics: How Many People Have Anal Fistulas?
Anal fistulas occur in as many as 8 out of every 10,000 people each year. In the Western Hemisphere, a small minority of cases are associated with Crohn's disease.
Anal fistulas happen twice as often in men than women. They're most common in adults around age 40, but they can occur in younger people, especially those with Crohn's disease.
Related Conditions
Some conditions cause symptoms that are similar to the symptoms of an anal fistula. They include:
- Anal fissure
- Anogenital warts (Condyloma acuminata)
- Hemorrhoids
- Rectal ulcers
- Crohn's disease
- Hidradenitis suppurativa
- Anal cancer
- STIs
The Takeaway
- Anal fistulas happen when an infection of the anal glands causes an abscess that tunnels through anal tissue to the skin outside the anus.
- Common symptoms of anal fistulas include pain, redness, and swelling around the outer opening, as well as drainage of pus, blood, and stool from that area.
- Most anal fistulas can only be repaired through surgery, though fistulas caused by Crohn's can sometimes resolve with IBD medication.
Common Questions & Answers
What are the warning signs of an anal fistula?
Common symptoms of an anal fistula include a visible opening near the anus with pus, blood, or stool draining from it; pain; redness; swelling around the opening; fever; chills; and feeling ill, among others.
What is the main cause of an anal fistula?
Anal fistulas are caused by the blockage, inflammation, and infection of the anal glands. This infection forms an abscess, and the pus and fluid inside collects and tunnels to the outside, forming a fistula.
What does an anal fistula look like?
An anal fistula looks like a small hole near the skin around your anus. It often looks red and swollen, and you may notice drainage coming from it.
How to cure anal fistula?
Anal fistulas are typically repaired through surgery, but they sometimes come back after complete healing.
Resources We Trust
- Cleveland Clinic: Anal Fistula
- Mayo Clinic: Anal Fistula: Symptoms and Causes
- Johns Hopkins Medicine: Anal Fistula
- American Society of Colon & Rectal Surgeons: Abscess and Fistula
- Cedars Sinai: Anal Fistula
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
- Anal Fistula. Cleveland Clinic. July 11, 2023.
- Anal Fistula - Symptoms and Causes. Mayo Clinic. July 2, 2024.
- Jimenez M et al. Anorectal Fistula. StatPearls. February 2, 2023.
- Anal Fistula. Johns Hopkins Medicine.
- Abscess and Fistula. American Society of Colon & Rectal Surgeons.
- Anal Fistula - Diagnosis and Treatment. Mayo Clinic. July 2, 2024.
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Ira Daniel Breite, MD
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Ira Daniel Breite, MD, is a board-certified internist and gastroenterologist. He is an associate professor at the Icahn School of Medicine at Mount Sinai, where he also sees patients and helps run an ambulatory surgery center.
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