An anal fistula can either be a single tunnel or, occasionally, a network of tunnels. It’s usually caused by an infection near the anus that causes pus to collect in the surrounding tissue. When the pus drains out, a tunnel or network of tunnels is left behind.
You’re more likely to develop an anal fistula if you’ve had an anal abscess, including a perianal abscess. About one in every two people with an anal abscess also develops an anal fistula.
An anal fistula requires fistula treatment, usually anal fistula surgery.
You may notice a small hole in the skin near your anus. You may also experience symptoms such as:
See your GP if you’re regularly experiencing any of the symptoms of an anal fistula. Your GP will ask about your symptoms and your general health, including any history of bowel conditions. With your permission, your GP may carry out a rectal examination. This involves examining your anus by gently inserting a gloved finger inside it.
If your GP diagnoses — or suspects — an anal fistula, they’ll refer you to a consultant called a colorectal surgeon. At your first appointment, your consultant may refer you for further investigations, including:
An anal fistula is often the result of an anal abscess (perianal abscess). A perianal abscess can occur when glands in your rectum that make fluids become blocked and then infected with bacteria — this causes the formation of a pus-filled abscess.
If the abscess becomes large enough, it can form tunnels that pass through the tissue around your rectum and out to the skin around your anus. As the abscess drains, it leaves a tunnel behind.
An anal fistula can also be caused by chronic bowel conditions, including:
In rare cases, complications after surgery near the anus, HIV and tuberculosis (TB) can cause an anal fistula.
Anal fistula treatment almost always involves anal fistula surgery to close the tunnel. This allows an anal fistula to heal without affecting your bowel continence.
The type of surgery recommended by your doctor will depend on the position of your fistula and whether it is one tunnel or a network of tunnels. Further examination may be needed to determine the most appropriate surgery — these investigations will be carried out under general anaesthetic.
Your consultant will discuss your options with you, which may include surgical procedures or a non-surgical procedure.
The most common type of fistula surgery is a fistulotomy. It involves opening the anal fistula by cutting along the length of it, so it closes and heals as a flat scar. A fistulotomy is effective for treating many anal fistulas but is only suitable for fistulas that do not pass through sphincter muscles as this reduces the risk of incontinence.
If your fistula passes through a considerable portion of your sphincter muscle and a fistulotomy will put you at a high risk of incontinence, your doctor may recommend an alternative surgery, such as:
Other surgical options include:
Fibrin glue offers the only non-surgical treatment and is not as effective as a fistulotomy. Under a general anaesthetic, a special glue is injected into your fistula to help it seal and heal. The results may not be long-lasting but this procedure may be recommended if your fistula passes through a considerable portion of your sphincter muscle.
The major risks of anal fistula surgery are:
Your level of risk after anal fistula surgery depends on the position of your fistula and the specific procedure used to treat it.
If an anal fistula is not treated correctly, you may experience anal abscesses more often and develop a complex network of anal fistulas. This may cause:
What causes an anal fistula?
An anal fistula often develops from an anal abscess (perianal abscess). A perianal abscess can occur when glands in your rectum that make fluids become blocked and then infected with bacteria — this causes the formation of a pus-filled abscess. If the abscess becomes large enough, it can form tunnels that pass through the tissue around your rectum and out to the skin around your anus. As the abscess drains, it leaves a tunnel behind — an anal fistula.
What does an anal fistula look like?
An anal fistula is a tunnel that develops between your bottom (anus) and your back passage (rectum). However, the tunnel is not visible from the outside. Instead, you may see a small hole in the skin of your bottom or something resembling an open boil.
How serious is a fistula?
An anal fistula can cause considerable discomfort and pain. If left untreated, it can also lead to complications, including:
Anal abscesses are caused by an infection with bacteria. In severe cases, a bacterial infection can worsen and lead to sepsis — this is a medical emergency.
If you are concerned that you have an anal fistula, see your GP.
What will happen if a fistula is left untreated?
If your anal fistula is not treated it can lead to complications, such as bleeding, bowel incontinence and pain. It can also increase your risk of recurring anal abscesses and anal fistulas. Abscesses are caused by infection and in severe cases, without treatment, they can lead to sepsis, which is a medical emergency.
There are lots of treatment options available for anal fistulas, depending on their position and whether your anal abscess is a single tunnel or a network of tunnels. See your GP to find out which treatment options are most appropriate for you.
How can I get rid of my fistula without surgery?
Anal fistula treatment almost always involves anal fistula surgery to close the tunnel. This allows an anal fistula to heal without affecting your bowel continence. However, in some cases, a non-surgical treatment called fibrin glue may be recommended by your doctor. This is not as effective as a fistulotomy, the most common anal fistula surgery, and is still carried out under general anaesthetic. It involves injecting a special glue into your fistula to help it seal and heal.
The results of fibrin glue treatment may not be long-lasting but may be recommended if your fistula passes through a considerable portion of your sphincter muscle. There are also other surgical options available if your fistula passes through your sphincter muscle, which will lower your risk of bowel incontinence.
How long does a fistula take to heal?
How long it takes your anal fistula to heal will depend on the type of treatment you have. Most treatments involve surgery but often, you will not need to stay overnight in hospital after your procedure. For those that do need to stay in hospital, this is usually just for a few days.
Your doctor will advise you on how best to manage your recovery. In general, it is important to rest for the first 24 hours after your surgery and avoid strenuous activities (eg exercise, heavy lifting) for about a week. In most cases, it will be several weeks before you can return to all of your normal activities.