Congenital Vascular Malformation

What is Congenital Vascular Malformation?

Congenital vascular malformations (CVMs) are growths or birthmarks made up of blood vessels that have not developed correctly. They occur in 1% of all births. Because they are rare, it is not easy to diagnose and treat them.

When the CVM is on the surface of the body, it is fairly easy to manage. Other types of CVMs can be more serious. This happens when they involve arteries, veins, and/or lymphatic vessels (part of the lymphatic system that helps protect us from infection and disease). CVMs can develop in any part of the body. They often occur on the hands and feet.

Types of Congenital Vascular Malformations (CVMs) 

“Vascular anomalies” is an all-inclusive term for vascular malformations, vascular tumors and other congenital vascular defects. The more commonly used term, Congenital Vascular Malformation (CVM), implies abnormally formed blood vessels that one is born with. However, in spite of its redundancy, CVM is a popular term and it will be used here.

Birthmarks occur on the surface of the body and are relatively easy to deal with. Other vascular malformations can develop from any type of blood vessel and develop in any part of the body, although most involve the extremities. They represent defects or development problems that occurred during embryonic growth. Depending on the state of development at the time this occurs, the result can involve arteries, veins, lymph vessels, or combinations of these.


Not all “birthmarks” are the same. Most are superficial and caused by abnormal collections of small blood vessels near the skin. This type of birthmark does not go away, and its size and appearance does not change. It is not a health threat and does not require treatment. It can be removed with a laser or covered up by a skin color tattoo, if desired. 

The other type of birthmark is a vascular tumor, or hemangioma. At first, it may appear similar to a birthmark on the surface of the skin. It will grow rapidly, then steadily get smaller. Most hemangiomas disappear completely in a few years (normally between ages 2 and 8). Treatment is usually not needed unless they cause problems with the eye, nose, or mouth. Most cases of childhood hemangiomas go away on their own. Parents can talk to their child’s doctor if they have questions about treatment options. Plastic surgery on the birthmark is an option when the child is grown. 

Venous CVMs

Half of CVMs occur entirely in the veins. There are two basic types of venous CVMs. Some appear as thin-walled lakes where blood collects. They may develop in grapelike clusters. This type of CVM does not usually affect the circulation of blood from veins to the heart. However, they can have an abnormal appearance and can interfere with daily activities. They also have the potential to host a type of non-serious blood clot (not the type that travels to the heart or lungs). These CVMs may be worth treating if they are large and cause problems, such as interfering with walking. 

The other type of venous CVM involves the deeper central veins. These CVMs often interfere with the veins’ function. Segments of major veins may be absent or narrowed. Conversely, some segments may be greatly widened and expanded. This is called a venous aneurysm. Treatment depends on how seriously the CVM affects blood flow from veins back to the heart, or whether it contributes to deep vein thrombosis (DVT). A DVT is a serious condition that occurs when a blood clot forms in a vein located deep inside the body. Most venous CVMs involve only short sections of veins and do not require treatment. 

Arterial-venous CVMs

An arteriovenous fistula (AVF) is an abnormal connection between an artery and a vein. When a cluster of them occurs, they are called arteriovenous malformations (AVMs). These are generally the most serious type of CVM. 

Blood typically flows from the arteries to capillaries and then into the veins. An AVF can lead to poor circulation. This is because it causes blood to bypass the capillaries and flow right from an artery to a vein. This means that blood is redirected away from tissues and organs. AVFs may also force the heart to work harder. 

AVFs are most common in the arms and legs, where they are easiest to manage. When they involve vessels in the hip/thigh region, brain or vital organs, treatment can be difficult. Although AVFs make up only one-third of all CVMs, they can cause the most serious problems. They are the type of CVMs most likely to require treatment. 

Arterial CVMs

CVMs of the arteries are the least common type. They make up only 1 to 2% of all cases. The most common arterial CVM occurs when a portion of an artery fails to develop. This causes blood to flow through an undeveloped side channel, called a collateral artery. If the collateral artery is compressed or injured, it could lead to an aneurysm or sudden clotting. 

Symptoms Of CVM

You can see or feel birthmark-type CVMs on the hands and feet. Varicose veins can be a cause of a CVM. Blood vessels that injure or bleed easily, or that lead to open wounds (ulcers) can cause a CVM. A limb can become enlarged or grow longer due to a CVM. An AVF may restrict circulation so that tissues and nerves do not get enough blood and oxygen, causing pain. 

How Is CVM Diagnosed?

In the past, the only sure way to evaluate blood vessel problems was by angiogram. That is a type of X-ray image taken after contrast dye is injected into the blood vessel. Since most CVMs do not need treatment right away, angiograms are now rarely needed as a first step. In addition, less invasive imaging is now available. CVMs found on the surface of the skin can often be viewed with a ultrasound imaging called a color duplex scan. Larger CVMs can best be studied by magnetic resonance imaging (MRI), which creates an image from multiple angles. MRI can help physicians see the extent of the CVM. An MRI also shows whether the CVM is near muscles, nerves, bones, or joints whose proximity might complicate treatment. 

Treatment Options

CVMs should be treated when they cause problems. Issues could include pain, ulcers, bleeding, blood clots, blockage of major blood vessels, or problems with the way limbs function. The timing of any treatment should be planned according to a child’s growth and development. It is often better to delay operating on very young children, if possible. 

In the past, surgery to remove a CVM was the only available treatment. Today, only about 10 to 15% of CVMs are surgically removed. Surgery can be risky— removing even the simplest CVM could lead to significant blood loss. Surgery may still be needed in some cases, but treatments using catheters have become more common. Catheters are placed into the lesions (usually through a groin vessel), and the abnormal vessels are embolized. That means they are blocked with injectable particles, substances, or devices. This technique can help prevent surgery or can shrink larger CVMs to make them easier to treat with surgery. 

Laser therapy may also work for small, localized birthmarks. Certain patients, such as those with Klippel–Trenaunay Syndrome, a rare venous malformation of the limbs, may benefit from compression garments and bandages. Surgery or less invasive therapy for enlarged superficial veins can also be helpful. 

Risk Factors

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