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Plastic and Reconstructive Surgery

Venous Malformations

Overview I Diagnosis I Treatment I Frequently Asked Questions 


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Venous malformations are slow-flow vascular malformations due to abnormalities in the development of veins.  Venous malformations vary in size and location within the body.  When the skin or tissues just under the skin are affected, they appear as a slightly blue-coloured skin stain or swelling.  These can vary in size from time to time because of swelling within the malformation.  As these are vascular malformations, these are present at birth and grow proportionately to the child.  As some venous malformations do not involve the skin and are deeply located, there may be no colour change or swelling in the skin and the condition is identified when a scan (such as MRI or ultrasound) is done.  

Ultrasound of a venous malformation in the muscle of the leg

Venous malformations can be very small to large in size and sometimes can involve a significant area within the body, such as an entire arm or leg.  When venous malformations involve much of the muscle in an arm or leg, there may be reduced circumference of the affected body part.  Venous malformations can involve the skin, mucous membranes (such as the lining of the inside of the mouth), tissues beneath the skin, muscles, joints and bones.  Venous malformations can also increase the size of the affected body part.  When the venous malformation is well localized, this may cause localized swelling, however, when the venous malformation is more extensive, there may be more widespread swelling of the affected body part.

Left: Venous malformation of the shoulder and upper arm with typical blue discolouration due to skin involvement. Right: Venous malformation of the hand and fingers, causing swelling.

Some patients with venous malformations have abnormal blood clotting within the malformation.  When a venous malformation is located within a joint, bleeding from the venous malformation into the joint can sometimes result in damage to the joint.  

Most venous malformations cause no life threatening problems for patients.  Some venous malformations cause repeated pain due to intermittent swelling and congestion of the malformation or due to the formation of blood clots within the malformation.  When a venous malformation involves an arm or leg, it is likely that the affected arm or leg will have good function. 

Rarely, venous malformations may be part of a syndrome (an association of several clinically recognizable features) or be linked to an underlying genetic abnormality.  


Patients with venous malformations who have involvement of the skin and mucous membranes can often be diagnosed by history and physical examination.  Venous malformations that are present in deeper locations are diagnosed on MRI and ultrasound scan.  These will confirm the diagnosis and provide excellent information regarding the extent of the abnormality.  Occasionally, other investigations such as blood testing are required.  Rarely, patients are referred for genetic counseling.  Venous malformations can sometimes be detected on antenatal scanning in a baby before birth.

Left: Venous malformation in the muscle of the upper arm causing swelling. Right: MRI scan of the same case.

Left: Blue skin stain in the leg due to a venous malformation. Right: MRI of the same case showing a large venous malformation in most of the muscle in the upper leg (arrow).




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There are several treatment options to consider for children with venous malformations.  Some children require no specific treatment as they may have no problems related to the venous malformation.  Unfortunately, there is no ‘quick fix’ for many venous malformations.  For children with extensive venous malformations, such as involving an entire arm or leg, wearing a compression garment may be recommended.  This helps reduce swelling and pain in many patients with extensive venous malformations.  Compression garments can also improve blood clotting abnormalities that can be seen sometimes in venous malformations.  

Radiological treatments called injection sclerotherapy can be undertaken to shrink the venous malformation and to help reduce pain.  These treatments are carried out by interventional radiologists in Image Guided Therapy.  To be effective, these treatments need to be repeated, usually at frequent intervals.  Sometimes, surgical excision of the venous malformation may be possible either without or following injection sclerotherapy.  For patients with frequent, disabling pain who have significant abnormalities of blood clotting seen on blood testing, blood thinner medication given by injection may be prescribed.  


More Pictures

A patient with venous malformation of the face.



Frequently Asked Questions

Why aren’t all venous malformations surgically removed?

Venous malformations can occur anywhere within the body and not all require specific treatment.  Many can be treated by injection sclerotherapy alone or in combination with surgery.  A few venous malformations may be suitable for surgical excision alone.  As venous malformations can involve skin, mucous membranes (such as the lining of the inside of the mouth), tissues beneath the skin, muscles, joints and bones, surgery may be difficult and injection sclerotherapy may be a preferred option.  As venous malformations can surround nerves and vital structures, surgery may not be an option.  

What do compression garments do?

Compression garments provide external support to the affected arm or leg.  This reduces the venous swelling in the venous malformation and thereby reduces pain.  Regularly wearing a compression garment can be very effective.  

How will I know the compression garment is working?

To see the benefits of wearing a compression garment, the garment must be worn consistently and daily for a few months.  It maybe advisable to gradually build up the length of time the garment is worn, in order to ensure tolerance of the garment.  If you have concerns regarding the fit of the garment, please contact the physiotherapist and the garment fitter within two weeks of receiving the garment.  

Wearing a compression garment can significantly reduce the pain and swelling in patients with a large or extensive venous malformation.  

I find the cost of continuously purchasing compression garments very expensive.  What should I do?

A compression garment is a medical device and your doctor at SickKids will provide you with a prescription for this.  Your insurance company may cover part of the cost of your compression garment and will likely require that a prescription be provided to them.  The physiotherapists at the Vascular Anomalies Clinic can provide you with more information about compression garments and other options that may be available for subsidizing their cost.  

Why does a venous malformation cause pain?

Pain can be due to swelling of the venous malformation.  This swelling may be due to engorgement of the venous malformation with blood.  The wall of the venous malformation is lacking in normal muscle cells and therefore stagnation of blood sometimes occurs.  Blood stagnation can lead to blood clots forming within the venous malformation which is another cause of pain.  

How will I know if the venous malformation involves muscles or joints?

This can sometimes be evident on physical examination.  Otherwise, the involvement will be evident on MRI and ultrasound scan.  X-ray of a joint can show evidence of advanced bone and joint damage.  

If a venous malformation has joint involvement, how can it be monitored for bleeding?  What should I do if I notice these signs?

Signs of bleeding within a venous malformation involving a joint are pain, being unable to fully move the joint, limping (if the malformation affects the legs or feet), an increased size of the joint and a feeling of warmth at the joint.  If you notice these signs, please call the Vascular Anomalies Clinic or your family doctor.  It is important to deal with bleeding in a joint promptly as there is a risk of joint damage.  

What should I do if I think I have a bleed into my joint from the venous malformation? 

It is important that you rest the affected joint until you have contacted your physician or the Vascular Anomalies Clinic.  

I noticed my affected arm or leg is smaller than the unaffected arm or leg.  Why does this happen?

This most often occurs because the venous malformation involves much of the muscle in the affected arm or leg.  This results in less than optimal growth and strength of the muscle.  Also, you may tend to favour the unaffected arm or leg causing a difference in muscle size and strength.  

Will I benefit from exercises for my smaller arm or leg?

Yes, you may benefit from strengthening exercises and activities.  This may not increase the muscle size but should improve the muscle function.  

What is the difference between a venous malformation and Klippel-Trenaunay syndrome?

A venous malformation is a slow flow vascular malformation and is one component of Klippel-Trenaunay syndrome (KTS).  A venous malformation can occur on its own, independently of KTS.  

KTS is a complex combined slow flow vascular malformation which most commonly affects a leg.  It has 3 components: a port-wine stain (a capillary malformation) in the skin, varicose veins (a type of venous malformation) and increased growth of bone or soft tissue (which for example can increase the length of an affected leg).  Lymphatic malformations including abnormalities of lymphatic flow may be present in KTS.  

Is a venous malformation associated with an increased risk of blood clots?

Yes, a venous malformation can be, however is not always, associated with an increased risk of blood clots.  Blood testing is useful in identifying patients who may have an abnormality of blood clotting in their venous malformation.  Many blood clots are small and some are only identified on scans such as magnetic resonance imaging and ultrasound and cause no problems.  Some patients who have frequent, troublesome pain and are identified on blood testing as having blood clotting abnormalities may be treated with blood thinning injections.  

Are blood clots within venous malformations life threatening?

It is rare that blood clots within the venous malformations move into the blood circulation and threaten life by blocking heart and lung circulation.  (A blood clot  blocking lung circulation is called a pulmonary embolism.)  

Is a venous malformation considered a disability?  (Do I qualify for disability benefits or services?)

A venous malformation may or may not be considered a disability.  This is evaluated on an individual basis.  

What can I do to deal with my venous malformation at school?

If your venous malformation affects your ability to write or use a keyboard or move between classes in the allotted time, it is encouraged that you speak to someone at your school about this.  A school may make arrangements to accommodate you and may require a medical note.  

Should I be participating in regular activities such as gym classes and sports?

Generally, yes, you will benefit from being as active as possible.  In certain cases, higher impact activities (for example, football, wrestling and skateboarding) may not be recommended.  The Vascular Anomalies Clinic physiotherapists can offer advice regarding activity risks, appropriate protective equipment and warm-up and cool-down exercises.  

How many injection sclerotherapy treatment sessions are needed to treat a venous malformation?

Usually, several injection sclerotherapy treatments are required.  This is to ensure that good closure of the malformation is achieved.  Treatments need to be at frequent intervals to prevent re-opening of the venous malformation.  The number of treatments is determined by the improvement in symptoms.  At SickKids, we initially arrange 3 injection sclerotherapy treatments at 6 week intervals and then decide if further treatment is required.  

After the age of 18, where are patients with venous malformations treated?

When you reach 18 years of age, if your care needs to be continued, the clinic will arrange transfer of care to an adult clinic in Toronto.  If, however, you do not need immediate transfer of care, the clinic will provide you with the necessary contact information for an adult clinic in Toronto.