Sclerotherapy is a procedure to treat different types of growths of the blood vessels. These growths are not cancer. They are called vascular malformations.

Vascular malformations are usually there from birth. They usually grow very slowly at first, but could grow quickly during puberty and pregnancy.

About half of vascular malformations can cause pain and swelling and changes to the colour of the skin at the affected area.

There is no cure for vascular malformations, but sclerotherapy treatment can improve the symptoms.

Sclerotherapy involves injecting special liquid or foam into your veins. This seals them closed. Most people have general anaesthetic and are asleep for the procedure.

It might take a few weeks to see results, and you might need more than 1 treatment.

Deciding to have sclerotherapy

Scans including MRI, CT, X-rays and ultrasound can diagnose vascular malformation.

The doctors will review these results to decide if sclerotherapy is the best treatment for you.

The only alternative treatment to sclerotherapy is surgery to remove the vascular malformation which may be suitable in some cases.  

Radiation and pregnancy

X-ray use a type of radiation known as ionising radiation. The dose used in medical X-rays is low, and the risks are small. The radiographer doing your X-ray will make sure your dose is kept as low as possible and that the benefits of having the X-ray outweigh any risk.

Radiation can be harmful for an unborn baby. If you are pregnant, or think you might be, you must tell a member of your medical team before your procedure.

We cannot do any procedure that involves radiation if you are pregnant or think you might be pregnant.

To make sure you are not pregnant, please use protection when you have sex, if there's a risk of you becoming pregnant from sex. You should use protection from the first day of your period until your appointment. If this has already passed, contact the department to reschedule your appointment so that it falls within the first 10 days of your period.

You will be asked to sign a pregnancy declaration form. 

Risks and side effects

Sclerotherapy is known to be safe and effective, but, as with any medical procedure, there are some potential side effects. We will discuss these with you at your clinic appointment.

Skin blistering and skin loss

If the vascular malformation is close to or just under the skin, there is a small risk of skin blistering and skin loss. If this happens it usually requires simple bandaging. In some cases it may require an operation to remove the affected area.

Nerve damage

If the vascular malformation is close to a major nerve, nerve damage may occur. This is usually like a bruise and will improve in a few days. Sometimes a permanent loss of feeling may occur. The doctor will consider this before deciding whether this type of treatment is the most suitable for you.

Vascular malformation continues to grow

There is a chance that the vascular malformation may not shrink or may even grow again later, in which case further treatment would be required. This will be decided when you visit the clinic for a follow-up appointment.

Allergic reaction

Occasionally, people may have an allergic reaction to the contrast we use when having an X-ray. 

These reactions could range from mild itching to severe reactions that can affect breathing or blood pressure. You will be continuously monitored during the procedure, so that any allergic reaction can be detected and treated immediately.


There is a small risk of thrombosis due to the foam bubbles passing through the blood circulation. It is a very rare complication.

We want to involve you in decisions about your care and treatment. If you decide to go ahead, you will be asked to sign a consent form. This confirms that you agree to have the treatment and that you understand what it involves.

You can read more about giving your consent.

Preparing for sclerotherapy

You will have general anaesthetic or sedation for this procedure. It's important that you have someone to escort you home and to stay with you for 24 hours following the procedure.

You can read more about having sedation or an anaesthetic.

Stopping eating and drinking

If you are having a general anaesthetic you will need to stop eating and drinking before your procedure. This is called fasting.

  • Do not eat or drink anything (except water) for 6 hours before the procedure.
  • You can have sips of water up to 2 hours before the procedure.


Please bring a list of all of your medicines into hospital with you so we can see exactly which ones you take. If you forget, you must tell us about any regular medicines you take. This includes anything you buy from a pharmacy or shop, and any herbal or homeopathic medicines. This can prevent delays to you receiving your usual medicines in hospital.

If you are taking any medicines that slow your blood clotting, tell your doctor or nurse as you might need to stop them temporarily before your procedure. These include:

  • antiplatelet medicines (such as aspirin or clopidogrel)
  • anticoagulant medicines (such as warfarin or rivaroxaban)

Also tell your doctor or nurse if you have:

  • any allergies to medicines
  • diabetes, as you might need to change the dose of your diabetes medicines. Let us know if you are taking metformin as this needs to stopped on the day of the procedure and 2 days afterwards.

Please continue to take your medicines as prescribed unless you have been told not to by a doctor or nurse. Do not make any changes to your usual medicines, or stop taking them, unless you have been told to do so.

More information about stopping any medicines will be given to you at your pre-assessment appointment.

If you have questions about your medicines, please ask a pharmacist or a member of your medical team. You can also call our pharmacy medicines helpline on 020 7188 8748 Monday to Friday, 9am to 5pm, email [email protected] (we try to respond to emails within 2 working days).

On the day of the procedure

The procedure will be carried out in interventional radiology department.

A nurse or doctor will check that your medical condition has not changed since your last appointment.

If you have any allergies or have previously had a reaction to the contrast that is sometimes used in sclerotherapy procedures, you must tell member of staff treating you.

We will explain the procedure to you and check that you understand. You can ask any questions you have. You will then be asked for your consent so that the procedure can go ahead.

General anaesthetic

Most people have a general anaesthetic so that you are asleep during the procedure. If you have a general anaesthetic you will not feel anything during the procedure. A doctor called an anaesthetist will explain this to you in detail.

Conscious sedation

Some people have sedation. This means that you will probably stay awake and be able to talk to the staff, but may not remember much about the procedure afterwards. We give you medicine to help you relax, then use local anaesthetic to temporarily numb the affected area. The local anesthetic might sting for a few minutes.

You should not feel any pain but let the nurse or doctor know if you feel uncomfortable so they can give you pain relief. You may have a warm sensation when the contrast is being injected, but this is not painful and goes away fairly quickly.

The procedure

We ask you to change into a hospital gown. We place a small cannula (thin tube) into a vein in your arm through which medicines will be given.

Once you are in the procedure room we ask you to lie on a bed, usually on your back. We attach you to a machine that monitors your blood pressure, heart rate, breathing and oxygen levels.

We use an ultrasound machine to see inside your body to check for the exact location of the vascular malformation.

We place several small needles in the vascular malformation. Sometimes a small amount of contrast is injected to confirm that the needles are in the right place. Then a liquid or foam, known as a sclerosing agent, will be injected. This causes the vascular malformation to shrink.

Often a course of injections is required. The number of injections will vary depending on the location, size and symptoms of the vascular malformation.

The procedure will be completed in less than an hour. Sometimes it is not possible to place a needle in a safe position, and we are unable to complete the procedure.

After the procedure

We take you to our recovery area where you will rest for a few hours. We do routine observations to check your pulse, blood pressure and the treated areas.

We'll offer you a light refreshment, such as tea or coffee, a sandwich and some fruit. If you have any special dietary requirements, you may wish to bring some food and drink with you.

A nurse will tell you when you can start moving and when you will be able to go home later that day.

You need a responsible adult to take you home by car or taxi. We do not recommend that you use public transport as you may feel unwell.

You will only need to stay overnight if you have pain and swelling that is not adequately controlled.

Recovery at home

You should arrange for a responsible adult to stay with you overnight. Get plenty of rest for the remainder of the day and possibly for the next day, depending on your recovery.

After the procedure it is quite normal to feel some discomfort from the treated areas, but this will reduce over the first few days after your operation.

You can shower 24 hours after the procedure, or have a bath 48 hours after. The treated area does not need to be covered.

You can resume your normal activities 48 hours after your procedure.


  • eat and drink normally
  • take your usual pain relief, as prescribed or instructed on the packet when needed
  • take your usual medicines, unless we give your special instruction
  • if you take any diabetes medicines containing metformin, do not take them for 2 days after sclerotherapy


  • do not drive
  • do not do any strenuous exercise for 48 hours to give the treated area time to heal

Pain and swelling

There will usually be pain and swelling after the procedure. The pain should get easier after a day or so, but the swelling may last up to 14 days.

Your doctor may advise you take regular paracetamol and anti-inflammatories like ibuprofen to help with the discomfort. These can be bought from your local chemist. You need only take them if you experience pain.

If the swelling has not gone down after 2 weeks, or if the skin breaks please contact us for advice.

When to get help

Contact us if you are worried about anything. Outside of our normal opening hours contact:

  • your GP
  • NHS 111

Go to A&E immediately if:

  • you notice swelling of your leg and foot, with or without pain
  • you have sudden chest pain or cough up blood

It is important that you tell the emergency doctors that you have had sclerotherapy treatment for vascular malformations.

They will want to know the date you were treated and any details about the treatment. Keep this information handy.

Follow-up appointment

The results are not immediate. The veins may look worse before it gets better and treatment may be repeated in 4 to 12 weeks.

One of our clinical nurse specialists (CNS) will call you 2 to 3 weeks after your procedure to discuss your recovery.

We will also send you an appointment for a follow up appointment with a doctor in 6 to 12 weeks after your procedure.

Resource number 4235/VER3
Date published March 2023
Review date March 2026

Contact us

If you have any questions or concerns after you have left hospital, please contact the interventional radiology department.

Phone: 020 7188 5525 for Guy's Hospital
Phone: 020 7188 5477 for St Thomas' Hospital

Monday to Friday, 9am to 5pm.

Do you have any comments or concerns about your care?

Contact our Patient Advice and Liaison Service (PALS)

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