Anal Fistula

An anal fistula is an abnormal tunnel connecting the inside of the anus to the skin outside, usually caused by an infected wound that drains pus. This painful condition affects everyday activities like sitting and walking, but with proper treatment, most people can return to normal life.

Table of contents

• What is an Anal Fistula?
• Other Names
• Associated Anatomy
• How Common is This Condition?
• Symptoms
• What Does It Look Like?
• Causes
• Risk Factors
• Diagnosis
• Treatment
• Recovery and Outlook
• Living With an Anal Fistula

fistula-in-ano, perianal fistula

What is an Anal Fistula?

An anal fistula is an abnormal passageway that develops from inside the anus to the skin outside^[1]. Think of it as a small tunnel that tracks from an opening inside the anal canal (the muscular opening at the end of the digestive tract where stool exits the body) to an outside opening in the skin near the anus^[4].

The condition usually develops in the upper part of the anus, where the anal glands are located. When these glands become infected, drainage from the infection can create a fistula^[1]. This is a chronic condition, meaning it is long-lasting and will not usually get better on its own^[3].

The fistula connects an infected anal gland or the anal canal to a hole in the outside skin around the anus. It originates from the anal glands, which are located between the internal and external anal sphincter and drain into the anal canal^[5]. If the outlet of these glands becomes blocked, an abscess can form which can eventually extend to the skin surface, and the tract formed by this process becomes a fistula^[5].

Other Names

An anal fistula is also called fistula-in-ano or a perianal fistula^[2]. “Perianal” means in the region of the anus^[1].

Associated Anatomy

• Anus
• Anal canal
• Rectum
• Anal glands
• Anal sphincter muscles
• Perianal skin

How Common is This Condition?

A fistula is a relatively common condition affecting the anus and rectum. It occurs twice as often in males as in females^[1]. The condition is most common in adults aged 30 to 50 years, with men being four times more likely to develop anal fistulas than women^[13].

About half of people who get an infected anal gland will develop a fistula. An infected gland that forms an abscess (a pocket of pus that needs to drain) causes 75% of anal fistulas^[1]. As many as 50% of people with an abscess get a fistula^[4].

Symptoms

The most common symptoms of an anal fistula include pain, swelling, and drainage^[1]. Understanding these symptoms can help you recognize the condition early and seek proper medical care.

Anal pain is often intense and throbbing. You may feel it more when you poop, cough, or sit. Your bottom may be sensitive to touch^[1]. The pain can be constant and may worsen with certain activities or movements^[3].

Swelling and redness (inflammation) appear inside or around the anus. These are signs of active infection under the skin, a condition called cellulitis^[1]. You may notice a red, inflamed area around the tunnel opening^[2].

Fluid drainage from somewhere around the anus is another key symptom. This drainage may include pus, poop, or blood (rectal bleeding). It may have an unpleasant smell^[1]. Some people experience oozing of pus, blood, or stool from the tunnel opening^[2]. The discharge can keep the area wet, leading to skin maceration (softening and breaking down of skin)^[5].

Less common symptoms include fever, pain when urinating, and difficulty holding in stool^[1]. Some people may experience pruritus ani (itching around the anus), tenderness, and chills, depending on the presence and severity of infection^[5]. In some cases, people may have difficulty controlling bowel movements, known as bowel incontinence^[3].

You may notice swelling and redness around your anus and a high temperature if you also have an abscess^[3]. You may or may not be able to see the fistula with a mirror^[1].

What Does It Look Like?

An anal fistula looks like a hole in the skin near your anus^[1]. The hole is actually the outermost portion of the tunnel, which connects to the abscess inside. It might ooze drainage, like pus, blood, or poop, especially when you touch the skin around it^[1].

The end of the fistula might be visible as a hole in the skin near your anus, although this may be difficult for you to see yourself^[3]. An opening on the skin around the anus may be visible during examination^[2].

Some older fistulas may close at the opening, while the rest of the tunnel remains. This causes pain and swelling until the fistula reopens to let out the drainage^[1]. If the fistula seals over, abscesses can recur, allowing the accumulation of pus, which can then extend to the surface again, repeating the process^[5].

Causes

The most common cause of an anal fistula is a perianal abscess, which usually forms over an infected anal gland^[1]. An abscess is a pocket of pus that develops at the site of an infection. The pus needs to drain away and may create its own drainage channel to the outside^[1].

Most anal fistulas are caused by an infection that starts in an anal gland. The infection results in an abscess that drains on its own or is drained surgically through the skin next to the anus. A fistula is the tunnel that forms under the skin along this drainage tract^[2].

Small glands just inside the anus are part of normal anatomy. If the glands in the anus become clogged, this may result in an infection. When the infection is serious, this often leads to an abscess^[4]. Bacteria, feces, or foreign matter can also clog the anal glands and cause an abscess to form^[4].

Sometimes, a healthcare provider creates a drainage channel to treat the abscess. But often, the wound doesn’t heal completely, leaving a fistula^[1]. An anal fistula often results from a previous or current anal abscess, and they can form when anal abscesses do not heal properly^[5].

Understanding how fistulas develop helps explain why they often occur when tissues are inflamed for a long time. Fistulas can occur throughout your body, either between different organs or from an organ to an opening in your skin. They usually occur when your tissues are inflamed for a long time, due to an injury or disease. Chronic inflammation and infection can eventually erode into the nearby tissues, especially when pus needs to drain. This can create a channel between the wound and nearby tissues^[1].

Less common causes of anal fistulas include:

• Inflammatory bowel diseases, such as Crohn’s disease^[1]
• Anal sexually transmitted infections (STIs)^[1]
• Tuberculosis affecting the anus^[1]
• A traumatic injury or previous surgery in the anus^[1]
• Radiation therapy for cancer in the pelvic region^[1]
• Actinomycosis, a rare bacterial infection that causes abscesses, sometimes in the perianal region^[1]
• Hidradenitis suppurativa, a chronic inflammatory skin disease that produces abscesses in sweat glands, occasionally in the perianal region^[1]
• Diverticulitis (infection of the small pouches that can stick out of the side of the large intestine)^[3]
• Infection with HIV^[3]
• A complication of surgery near the anus^[3]

Risk Factors

You’re more likely to get an anal fistula if you are male^[1]. Having an anal abscess raises your risk of having an anal fistula^[6].

Certain conditions of the lower digestive tract or anal area may also raise your risk. These include colitis, Crohn’s disease, chronic diarrhea, and previous radiation treatment for rectal cancer^[6]. Crohn’s disease, cancer, trauma, and radiation can increase the risk of infections and fistulas^[4].

Diagnosis

If you have symptoms that seem like an anal fistula, your healthcare provider may refer you to a specialist for colon and rectal diseases^[1]. Most anal abscesses or fistulas are diagnosed and managed based on clinical findings^[4].

To diagnose an anal fistula, your health care provider will discuss your symptoms and do a physical exam^[8]. The specialist will ask about your symptoms and your health history. During your physical exam, the provider will look for a fistula opening near your anal opening^[1]. They may press on the area to see if it’s sore and if pus comes out^[4].

The provider may also ask to examine the area around and inside your anus. This involves gently inserting a gloved finger into your bottom, called a rectal examination^[3]. The external opening of an anal fistula is usually easily seen on the skin around the anus. Finding the fistula’s internal opening inside the anal canal is more complicated^[8].

Sometimes, you’ll need to have a special exam under anesthesia so the provider can get more information without causing you pain^[1]. A colon and rectal surgeon may recommend anesthesia during an examination of the fistula. This allows for a thorough look at the fistula tunnel and can identify any possible complications^[8].

Knowing the complete path of an anal fistula is important for effective treatment^[8]. Different methods may be used to help with the diagnosis:

Fistula probe: A long, thin probe (narrow instrument) is guided through the outer opening of the fistula. In this way, it may be possible to find both openings. A special dye may be injected to find out where the fistula opens up^[1]. An instrument specially designed to be inserted through a fistula is used to identify the fistula tunnel^[8].

Anoscopy: This is a special scope (small endoscope) used to look inside your anal canal^[1][8].

Proctoscopy: A special telescope with a light on the end is used to look inside your anus^[3].

Imaging tests: These may include an ultrasound, which creates an image of the anal area using sound waves. Or they may include an MRI (magnetic resonance imaging), which makes images of the area by using special magnets and a computer^[1]. MRI can map the fistula tunnel and provide detailed images of the sphincter muscle and other structures of the pelvic floor^[8]. Endoscopic ultrasound, which uses high-frequency sound waves, can identify the fistula, the sphincter muscles and surrounding tissues^[8].

Fistulography: This is an X-ray of the fistula that uses an injected contrast to identify the anal fistula tunnel^[8].

Flexible sigmoidoscopy or colonoscopy: These procedures use an endoscope to examine the large intestine (colon). Sigmoidoscopy can evaluate the lower part of the colon. Colonoscopy, which examines the full length of the colon, is important to look for other disorders, especially if ulcerative colitis or Crohn’s disease is suspected^[8].

Occasionally, imaging studies such as ultrasound, CT scan, or MRI can help in the diagnosis and management of deeper abscesses and may be used to visualize the fistula tunnel^[4].

Treatment

Anal fistulas usually require surgery as they rarely heal if left untreated^[3]. Surgery is the primary treatment^[1]. Once you have an anal fistula, antibiotics alone won’t get rid of it. You’ll need to have surgery to treat the fistula^[6].

Antibiotics alone are not effective in treating abscesses or fistula. Antibiotics may be needed, in addition to surgery, if a patient has immunity issues, specific heart valve conditions, or widespread cellulitis^[4].

The main surgical options depend on the position of your fistula and whether it’s a single channel or branches off in different directions^[9]. The aim of surgery is to heal the fistula and avoid damaging the sphincter muscles (the ring of muscles that open and close the anus). Damaging the sphincter muscles could potentially result in loss of bowel control (bowel incontinence)^[9].

Surgery for an anal fistula is usually carried out under general anaesthetic (where you’re asleep). In many cases, it’s not necessary to stay in hospital overnight afterwards^[9]. Many people do not need to stay in hospital overnight after surgery, although some may need to stay in hospital for a few days^[3].

The main surgical procedures include:

Fistulotomy: This is the most common type of surgery for anal fistulas. This involves cutting along the whole length of the fistula to open it up, so it heals as a flat scar^[9]. A fistulotomy is the most effective treatment for many anal fistulas, but it’s usually only suitable for fistulas that do not pass through much of the sphincter muscles, because the risk of incontinence is lowest in these cases^[9]. During this surgery, the fistula track will be opened to allow healing from the bottom up^[4].

Seton procedures: If your fistula passes through a significant portion of anal sphincter muscle, the surgeon may initially recommend inserting a seton. A seton is a piece of surgical thread that’s left in the fistula for several weeks to keep it open^[9]. This allows it to drain and helps it heal, while avoiding the need to cut the sphincter muscles. Loose setons allow fistulas to drain, but do not cure them. To cure a fistula, tighter setons may be used to cut through the fistula slowly^[9]. The seton drain can help relieve symptoms and mark the fistula for doctors to fix later. It may stay in place for 6 weeks or longer^[18].

Advancement flap procedure: An advancement flap procedure may be considered if your fistula passes through the anal sphincter muscles and having a fistulotomy carries a high risk of causing incontinence. This involves cutting or scraping out the fistula and covering the hole where it entered the bowel with a flap of tissue taken from inside the rectum. This has a lower success rate than a fistulotomy, but avoids the need to cut the anal sphincter muscles^[9].

LIFT procedure: The ligation of the intersphincteric fistula tract (LIFT) procedure is a treatment for fistulas that pass through the anal sphincter muscles, where a fistulotomy would be too risky. During the treatment, a cut is made in the skin above the fistula and the sphincter muscles are moved apart. The fistula is then sealed at both ends and cut open so it lies flat. This procedure has had some promising results so far, but it’s only been around for a few years, so more research is needed^[9].

Endoscopic ablation: This is where an endoscope (a long, thin tube with a small camera on the end) is put in the fistula. An electrode is then passed through the endoscope and used to seal the fistula. Endoscopic ablation works well and there are no serious concerns about its safety^[9].

Laser surgery: Radially emitting laser fibre treatment involves using a small laser beam to seal the fistula. There are uncertainties around how well it works, but there are no major safety concerns^[9].

Fibrin glue: Treatment with fibrin glue is currently the only non-surgical option for anal fistulas. It involves the surgeon injecting glue into the fistula while you’re under a general anaesthetic. The glue helps seal the fistula and encourages it to heal. It’s generally less effective than fistulotomy for simple fistulas and the results may not be long-lasting^[9].

Bioprosthetic plug: This is a cone-shaped plug made from animal tissue that’s used to block the internal opening of the fistula. This procedure works well for blocking an anal fistula and there are no serious concerns about its safety^[9].

Recovery and Outlook

Most people can go back to work and their normal routine 1 to 2 weeks after surgery^[1]. It will probably take several weeks to several months for your fistula to completely heal. This depends on the size of your fistula and how much surgery you had^[1].

After surgery, patients typically take about 5 to 6 weeks to recover. During this time, patients should rest and avoid strenuous activities that could disrupt the surgical site^[13]. Rest when you feel tired. Getting enough sleep will help you recover. Be active. Walking is a good choice. Most people are able to return to work within 1 to 2 weeks after surgery^[18].

You may be worried about having a bowel movement after your surgery. You will likely have some pain and bleeding with bowel movements for the first 1 to 2 weeks^[18]. Pain-relief medications may be prescribed to manage discomfort in the anal area^[13]. Take pain medicines exactly as directed^[18].

You may notice a small amount of pus or blood draining from the opening of your fistula. This is normal in the days after your surgery. You can put a gauze pad over the opening of the fistula to absorb the drainage, if needed^[18]. Place a maxi pad or gauze in your underwear to absorb drainage from your fistula while it heals^[18].

After a bowel movement, use a baby wipe or take a shower or sitz bath to gently clean the anal area^[18]. Sit in 8 to 10 centimetres (3 to 4 inches) of warm water (sitz bath) for 15 to 20 minutes. Then pat the area dry. Do this as long as you have pain in your anal area^[18].

A diet rich in fiber should be incorporated to support healthy digestion and prevent constipation, reducing strain during bowel movements^[13]. You can make your bowel movements less painful by getting enough fibre and fluids, and using stool softeners or laxatives^[18].

Unfortunately, despite proper treatment and complete healing, an abscess or a fistula can come back. If an abscess comes back, it suggests that perhaps there is a fistula that needs to be treated. If a fistula comes back, additional surgery will likely be required to treat the problem^[4].

Living With an Anal Fistula

While surgery is the main treatment, certain daily care strategies can help manage symptoms and maintain comfort, especially while waiting for treatment.

Sitz baths can work wonders. Soaking your anal area in warm water for 10 to 15 minutes, 2 to 3 times daily, can reduce inflammation, soothe pain, and keep the area clean^[16]. Sitting in warm water after bowel movements will also help^[18].

Maintaining proper hygiene is crucial. Keep the affected area clean and dry. Use fragrance-free, alcohol-free wipes or a bidet after bowel movements. Avoid harsh soaps or aggressive wiping, which can worsen symptoms. Pat the area dry with a soft, clean towel to avoid moisture buildup^[16].

Managing pain and discomfort: Avoid prolonged sitting; use a cushion or donut pillow to reduce pressure on the anus^[16][20]. Support your feet with a small step stool when you sit on the toilet. This helps flex your hips and places your pelvis in a squatting position. This can make bowel movements easier^[18].

Maintaining soft, regular bowel movements is important. Hard stools or straining can aggravate a fistula. Aim for smooth digestion with a high-fiber diet (25 to 30 grams daily) including fruits, vegetables, and whole grains. Drink 8 to 10 glasses of water daily to keep stools soft^[16]. Include high-fibre foods, such as fruits, vegetables, beans, and whole grains, in your diet each day. You may want to take a fibre supplement every day^[18].

Living with an anal fistula can create emotional challenges. The persistent discomfort, unexpected flare-ups, and emotional toll can make daily life challenging^[16]. For people with chronic conditions like Crohn’s disease who also develop a perianal fistula, life becomes an even more arduous journey filled with physical and emotional struggles^[19]. It’s important to seek support and maintain open communication with your healthcare provider about both physical symptoms and emotional well-being.