Understanding Anal Fistulas: Symptoms, Causes, Diagnosis, and More

Whether you are dealing with an anal fistula yourself or simply want to be better informed about this health condition, our aim with this article is to provide you with clear, accurate information.

You can also find out more about the specifics of anal fistula surgery here.

• What is an anal fistula?
• What are the symptoms of an anal fistula?
• What causes anal fistula?
• What does an anal fistula look like?
• Are anal fistulas common?
• Are anal fistulas dangerous?
• Are anal fistulas painful?
• Can anal fistula cause cancer?
• How is an anal fistula treated?

What is an anal fistula?

An anal fistula is a small tunnel that develops between the end of the bowel, known as the anal canal, and the skin near the anus. This is a result of an infection near the anus causing a collection of pus (an abscess) in the nearby tissue. When the abscess drains, it can create a small tunnel or passageway – the fistula.

What are the symptoms of an anal fistula?

If you or someone you know is concerned about the possibility of an anal fistula, being informed about the symptoms is a good first step. Although only a healthcare provider can provide a definitive diagnosis, understanding the symptoms can help you decide when to seek medical advice. Below is an in-depth guide to the symptoms of an anal fistula:

Pain and Discomfort
One of the most common symptoms of an anal fistula is persistent pain in the anal region. This pain can be constant or it might intensify during certain activities like bowel movements, sitting, walking, or coughing. It’s often described as a throbbing pain.

Swelling and Redness
The area around the anus may become swollen or inflamed due to an anal fistula. There may be visible redness, and the skin may feel warm or hot to the touch.

Abnormal Discharge
You may notice an abnormal discharge from the area around the anus. This discharge can be pus, blood, or a combination of the two. It may be accompanied by a foul smell, which is a sign of infection.

Irritation and Itching
The abnormal discharge from the fistula can lead to irritation and itching in the skin around the anus. This can result in a feeling of discomfort and an urge to scratch the area.

Frequent Anal Abscesses
If you’re having recurring anal abscesses, it could indicate the presence of an anal fistula. An abscess is a painful collection of pus, and once it’s drained, a fistula may form.

Fever and General Malaise
In some cases, especially when the fistula or associated abscess is significantly infected, you might experience systemic symptoms like a fever, chills, fatigue, or a general feeling of being unwell.

Difficult or Painful Bowel Movements
An anal fistula can make bowel movements painful or difficult. You might experience a sharp pain during and after passing stools.

It’s essential to understand that the symptoms can vary in severity and can change over time. You may not experience all the symptoms mentioned above, and the symptoms can come and go.

Keep in mind that many of these symptoms can also be associated with other conditions, so it’s crucial not to self-diagnose. If you’re experiencing any of the symptoms listed, especially if they’re persistent or causing you distress, please seek medical attention. Your healthcare provider can provide a thorough examination and appropriate testing to reach an accurate diagnosis.

What causes anal fistula?

You may be asking ‘how do you get an anal fistula?’. Anal fistulas are most often caused by an infection in an anal gland that spreads to the skin. Once the infection forms an abscess (a swollen area filled with pus), it can tunnel through the tissue to create a fistula. Let’s delve into the various causes and risk factors that could contribute to the formation of an anal fistula.

Anal Abscesses
This is the most common cause of an anal fistula. Abscesses can occur when the small glands inside the anus become blocked. Bacteria, faecal matter, or foreign matter can clog these glands, leading to an infection. When the abscess drains, either naturally or via surgical intervention, it can result in a fistula.

Crohn’s Disease
This is a type of inflammatory bowel disease (IBD) that causes chronic inflammation of the gastrointestinal tract. If the inflammation affects the anal area, it can lead to abscess and fistula formation.

Diverticulitis
This condition occurs when small, bulging pouches (diverticula) that can form in the lining of the digestive system become inflamed or infected. This can result in abscess formation, which could subsequently lead to a fistula.

Surgery Near the Anus
Any surgical procedure in the anal region, such as removal of an anal fissure, hemorrhoid, or abscess, can potentially lead to fistula formation if the surgical wound becomes infected.

Tuberculosis (TB)
In rare cases, a form of TB affecting the intestines can lead to the formation of an anal fistula.

Sexually Transmitted Infections (STIs)
Certain STIs like HIV and syphilis can increase the risk of an anal fistula.

Cancer
In rare cases, anal or rectal cancer can cause a fistula.

Radiation therapy
Radiation therapy used in the treatment of various types of cancers in the pelvic area can sometimes cause fistulas.

Trauma
Trauma or injury to the anal area could potentially lead to a fistula.

Remember, although these are potential causes, not everyone with these conditions or situations will develop an anal fistula. The body’s response to infection and individual health status, among other factors, play a significant role in fistula formation.

If you’re experiencing symptoms that you suspect could be due to an anal fistula, it’s crucial to seek medical advice. Early detection and treatment can help manage the condition effectively and potentially reduce complications.

What does an anal fistula look like?

An anal fistula, being an internal condition, isn’t easily visible without medical examination. However, you might be able to see some external signs depending on where the fistula opens onto the skin surface.

A visible opening or small hole near the anus is a typical external sign of an anal fistula. This hole might be surrounded by swollen, red, or irritated skin. It could discharge pus, blood, or a mix of the two, and this might result in staining of undergarments. The discharge may also have an unpleasant odour due to the presence of infection.

In some cases, an anal fistula may cause a visible lump or swollen area around the anus, particularly if an abscess is present or reoccurring.

It’s important to note that not all anal fistulas will have visible signs or symptoms. Some fistulas might be internal and only open inside the anal canal or rectum, while others may present symptoms intermittently. This is why a medical examination by a healthcare professional, and in some cases imaging studies like an ultrasound or MRI, are essential for a definitive diagnosis.

If you’re noticing changes or discomfort in your anal area, it’s always a good idea to seek medical advice. These symptoms can also be associated with other conditions like haemorrhoids, anal fissures, or certain types of infections. A healthcare professional can help determine the cause and recommend appropriate treatment.

Are anal fistulas common?

Anal fistulas are relatively common, especially among individuals with certain risk factors. They occur in about 2 to 4 out of every 10,000 people, which may seem relatively low, but they’re fairly common in colorectal surgery practices and among individuals with specific conditions.

People with a history of anal abscesses are particularly susceptible to developing anal fistulas, as up to 50% of people who have an anal abscess may eventually develop a fistula. Also, those with inflammatory bowel disease (IBD), especially Crohn’s disease, have a heightened risk of anal fistula. It is estimated that up to one-third of people with Crohn’s disease will develop a fistula at some point.

Are anal fistulas dangerous?

How serious is an anal fistula? Anal fistulas themselves are not typically life-threatening, but they can cause significant discomfort and affect the quality of life. Moreover, they seldom heal by themselves and usually require medical treatment to prevent complications.

Untreated, an anal fistula can lead to a range of complications such as:

Recurrent Abscesses
The fistula can become blocked, leading to the recurrent formation of abscesses. These can be painful and may require surgical drainage each time.

Spread of Infection
The infection can spread to surrounding tissues, causing cellulitis (a skin infection) or sepsis, a serious bloodstream infection that can be life-threatening.

Faecal Incontinence
If a fistula crosses the sphincter muscles – the muscles that help control bowel movements – it can potentially lead to issues with bowel control, known as faecal incontinence.

Anal Cancer
While quite rare, chronic inflammation in the anal area due to fistulas could potentially increase the risk of developing anal cancer over time.

Impact on Mental Health
The symptoms of an anal fistula, along with the potential for recurrent abscesses and ongoing pain, can impact mental health, leading to anxiety or depression in some people.

Are anal fistulas painful?

Yes, anal fistulas can often be painful. The degree of discomfort can vary from person to person, but it is generally described as a constant, throbbing pain in the anal area. The pain can become worse during bowel movements, while sitting, walking, or coughing.

The discomfort is mainly due to the inflammation and infection associated with the fistula and potential abscess formation. The fistula tunnel itself and the skin around the external opening of the fistula can also become irritated, leading to further discomfort.

However, it’s important to note that not all anal fistulas cause pain. Some may be relatively asymptomatic, especially if they are not infected. Other symptoms, such as abnormal discharge from the anus, itching, irritation, and recurrent anal abscesses, can also be present with or without pain.

If you’re experiencing persistent pain in the anal area or any other symptoms suggestive of an anal fistula, it’s essential to seek medical advice. Effective treatments are available that can alleviate the pain and treat the fistula.

Can anal fistulas cause cancer?

Anal fistulas themselves are not directly known to cause cancer. However, having a chronic anal fistula can lead to persistent inflammation in the anal area, and in rare instances, long-term inflammation has been linked to an increased risk of developing certain types of cancer, including anal cancer. Still, this association is relatively rare and other factors, such as human papillomavirus (HPV) infection, are more commonly linked to anal cancer.

It’s also important to note that certain symptoms, such as bleeding, pain, or a lump near the anus, can be common to both anal fistulas and anal cancer. So, it’s crucial that any symptoms are evaluated by a healthcare provider to reach the correct diagnosis.

Additionally, certain conditions that can cause anal fistulas, such as Crohn’s disease, have also been associated with a slightly increased risk of developing colorectal cancer over time, compared to the general population. This risk is related more to the severity and duration of inflammation in the intestines rather than the presence of fistulas.

Are anal fistula hereditary?

Anal fistulas are not considered to be hereditary. They are typically caused by an infection or inflammation that leads to an abscess in the anal region, which can then develop into a fistula.

How is an anal fistula diagnosed?

You may be asking: ‘do I have an anal fistula?’ and ‘how is it diagnosed?’.

Diagnosing an anal fistula involves several steps and often requires more than one type of test or procedure. Here’s an in-depth look at the process:

Medical History and Physical Examination
The first step in diagnosing an anal fistula involves a thorough medical history and physical examination. Doctors will ask about your symptoms, their duration, and any prior relevant medical issues, like anal abscesses or conditions like Crohn’s disease. A physical examination will involve a visual inspection of the area around your anus. Doctors will be looking for signs like swelling, redness, or an external opening of a fistula.

Digital Rectal Examination (DRE)
During a DRE, your doctor will gently insert a lubricated, gloved finger into your rectum to feel for abnormalities. This exam can help determine if there’s a tract or opening in the rectal area, which could suggest a fistula.

Anoscopy
An anoscopy is a procedure that involves using a small, tubular instrument called an anoscope to examine the inside of the anal canal and lower rectum. This can help your doctor identify internal openings of a fistula or other abnormalities.

Endoanal Ultrasound
This is a type of ultrasound test specifically used to examine the anal and rectal areas. A small ultrasound probe is inserted into the anus and used to create images of the surrounding tissues. It can help your doctor see the fistula tract and determine its course and depth.

Magnetic Resonance Imaging (MRI)
An MRI uses magnetic fields and radio waves to create detailed images of the body’s structures. An MRI of the pelvis can provide a clear picture of the fistula and surrounding tissues, which can be particularly helpful if the fistula is complex or if other diagnostic tests have been inconclusive.

Fistulography
This is a type of X-ray procedure where a contrast dye is injected into the suspected fistula tract, which is then imaged using X-rays. The dye helps to highlight the fistula tract and show its depth and direction.

Computed Tomography (CT) Scan
While not as commonly used as some of the other tests, a CT scan, which uses a series of X-ray images to create detailed cross-sectional images of the body, can be used in some cases to help diagnose a fistula.

While these diagnostic tests can provide valuable information, the exact diagnosis and treatment plan will depend on your individual symptoms, health history, and the complexity of the potential fistula. Therefore, it’s essential to have an open discussion with your healthcare provider about your symptoms and concerns.

How is an anal fistula treated?

Anal fistulas don’t go away on their own without treatment.The first step is to treat the underlying cause, which will involve diagnostic tests such as those detailed above.

If there is evidence of an abscess, you may require antibiotics or surgery to drain the pus. Typically fistulas require surgery to repair them, and it is not uncommon to require multiple treatments.

Your doctor may recommend the following surgical options:

Fistulotomy
The fistula is cut open so it can heal (this will leave a flat scar)

The seton procedure
A surgical thread is left in the fistula, usually for several months. This allows the pus to drain out and the infection to settle down. A follow-up procedure will often be required to definitively treat the fistula

A ligation of internal fistula tract (LIFT) procedure
The fistula tract is divided between the muscles of the bottom

Video-assisted anal fistula treatment
The surgeon uses an endoscope light to see inside the anal fistula tract and locate the internal opening.

Other options include fibrin glue, a fistula plug, ligation or an endorectal advancement flap.

More information

• If you’re struggling with pain, speak to your GP in the first instance. (Don’t have a GP?)
• You can also self-refer to one of our expert psychologists or psychiatrists.