Perianal abscess and fistula
This page gives you information about infections around your anus (bottom) known as perianal abscesses. Also included is information about fistulae (abnormal connections) that can happen in this area.
What is a perianal abscess?
An abscess is a collection of pus that is usually caused by infection. When this happens around your anus (bottom) it is called a perianal abscess. The pus is usually made up of dead skin cells, white blood cells (which fight infection) and dead bacteria.
Perianal abscesses usually occur when one of the glands inside your bottom becomes infected with bacteria.
Patients with inflammatory bowel disease such as Crohn’s are at higher risk of developing perianal abscesses.
Treatment options
No treatment
Sometimes, infections around your bottom can be cleared by your body with the aid of sitz baths (sitting in a bath with salt in the water), to help to keep the area clean.
However, when an infection has developed into an abscess, it is more unlikely for your body to be able to clear it without medical intervention.
Antibiotics
These can be used to treat infection that has developed into an abscess with varying degrees of success. If the antibiotics do not make your symptoms better, it may be necessary to consider surgery. Sometimes abscesses come back if they have not been cleared completely with antibiotics.
Surgery
You may be offered a procedure called ‘examination under anaesthetic (EUA) and incision and drainage’. This aims to clean out the infection and help the wound to heal.
About the surgery
This surgery is usually carried out using a general anaesthetic (while you are asleep). The surgeon will examine your bottom (anus and rectum) while you are asleep. A cut will then be made in the skin to allow the pus to drain from the abscess.
It is important that the cut is big enough to drain all of the pus from the cavity. This is because we want the skin wound to remain open while the cavity underneath closes up. If the skin closes too quickly then abscesses can recur.
Although it may be alarming to think of an open wound so near to your bottom, the skin in this area is adapted to being near poo and the wounds very rarely get infected. You should keep the area clean by showering the wound or using a wet flannel after having a poo.
The cavity where the pus was will be cleaned out with salty water and sometimes packed with a material (called aquacel) which helps to prevent further bleeding. The packing is not always needed but may be used if the cavities are very large and are bleeding.
The packing can be removed after 24 to 48 hours by the practice nurse at your GP’s surgery but do not worry if it falls out before then.
Your wound will be left open and will not usually need any dressings.
You will be able to carry on with your normal daily activities but we recommend that you use a sanitary/ hygiene pad (available from a supermarket or pharmacy) to protect your underwear.
Up to 85 out of every 100 people who have an abscess drained do not have any problems once the cavity has healed. A number of people, about 15 out of every 100, might continue to have occasional discharge. This suggests that there may be a fistula and is explained in more detail towards the end of this page.
Risks of the surgery
Pain - you can take pain relief such as paracetamol and ibuprofen if you have not been told otherwise. The pain should get better gradually over 1 to 2 weeks after the surgery. You can take stronger painkillers such as codeine but these do cause constipation which make your pain worse so they should only be taken occasionally and you may need laxatives with them.
Infection in wounds – this is uncommon.
Bleeding - this can be inside the cavity or on the surface from the cut made in the skin.
Scar – the size of the scar is dependent on the size of the abscess. A larger abscess requires a larger cut to allow easy drainage of all of the pus.
Recurrence – even after the abscess has been washed out, a few bacterial cells may remain inside the cavity. These cells can multiply and lead to another abscess forming in the same place. Abscesses in certain areas (for example that have collected between the muscles around your bottom) can sometimes be more challenging to drain and you might need a further procedure. If you are prone to perianal abscesses, for example from an inflammatory bowel disease such as Crohn’s, you may be at risk of developing more abscesses in this region. To reduce your risk, you should avoid smoking and if you have diabetes, you should make sure that your blood sugar is well controlled.
Anaesthetic – this can cause complications such as nausea and vomiting after the surgery or rare complications such as a blood clot in your legs or lungs (deep vein thrombosis/DVT)
What happens if I am offered surgery?
When you are seen on the Surgical Assessment Unit, the doctor will explain the procedure. You will then be asked to sign a consent form stating that you understand why you are having the surgery and you are willing to go ahead with the procedure. This is a good opportunity to ask any questions you may have.
If you are seen on the Surgical Assessment Unit early in the day, it might be possible to carry out the operation on the same day. Alternatively, you may be asked to return the following morning.
If you are asked to return you will be given fasting instructions which means you should not have anything to eat or any milky drinks for 6 hours before the operation. This means that you must not have anything to eat after 2:00am on the morning of your surgery. You can only have sips of water up until 6:00am then you must not have anything to eat or drink.
You should then return to the Surgical Assessment Unit on Ward 5b at 7:30am for the operation.
Your operation will be on an emergency list, so there is a chance that it may be delayed or cancelled if someone with a more urgent problem needs an operation before you.
What to expect after the operation
- You are likely to be able to go home the same day as your operation. You must make sure that you have someone to escort you home and a responsible adult to be with you for 24 hours after you have had the anaesthetic.
- You are not likely to need antibiotics after the operation.
- Your wound will be left open. You can make an appointment with the practice nurse at your GP’s surgery to have the packing removed after 24 to 48 hours.
- You can do gentle exercise when you feel well enough after the operation but you should wait for 1 month before returning to more strenuous exercise or activities.
- Going back to work will depend on how your wound heals, how you respond to surgery and the type of job you do. In most cases, it is usually safe to return to work 10 to 14 days after the operation. Please let a member of staff in the unit know if a work certificate or sick note is required. If you forget this then you should ask your GP to provide one.
What is a perianal fistula?
A fistula is an abnormal connection between two parts of your body which are not normally connected. With a perianal abscess this means that a fistula can develop between the abscess cavity (where the pus has drained from) and inside at the top of your anus (which is usually about 3 cm long and is surrounded by your sphincter muscle which is what you squeeze to stop yourself from pooing).
If there is suspicion of a fistula between the abscess cavity and your anal canal, you may require further investigations after the operation. This may include an MRI scan so that the surgeon can see exactly where the connection is. This will allow them to plan further surgery to treat the fistula.
Discharge advice
If after discharge you develop any of the following, please contact your GP or NHS 111 for advice:
- you develop a fever.
- your wound seems infected (worsening pain, pus coming out of the wound).
- your pain is not improved by simple pain relief such as paracetamol or ibuprofen.
Contact information
In an emergency, please contact 999.