Venous malformations comprise either superficial or deep veins that are abnormally formed and dilated. The walls of these vessels are thin because they lack smooth muscle.

Venous malformations are the most common type of vascular malformation. Although they usually are present at birth, they may not be seen until years later.

Although the exact cause of these lesions has not yet been determined, a deficiency of smooth muscle cells in the vein walls is known to be a critical factor. There is no evidence that drugs or medications taken during pregnancy, or environmental exposures that may have occurred during that time can cause venous malformations. There have been some families identified with multiple venous malformations that have alterations in the genes responsible for the communication of endothelial cells and smooth muscle.

These lesions may be present in the skin, mucous membrane or in any organ system, including the brain, bowel, liver, or spleen.

Venous malformations can be superficial or deep or can have both superficial and deep components. They can also be localized or diffuse and can occur in more than one site. Their color depends upon the depth and amount of expansion in the affected vessels. The closer these vessels are to the surface, the deeper the color. A superficial lesion thus tends to be maroonish-red, whereas a deep lesion may show a bluish hue. A very deep lesion may have no color, but just reveal itself as a protruding mass.

Venous malformations are soft to touch. When they are compressed, the color changes as the blood empties out. When your child cries or is lying down, the lesion expands, the blood vessels fill, and the color becomes more intense. Venous malformations swell when the area involved is lowered below the level of the heart (a dependent position). Also, lesions that are in the head/neck region enlarge when the patient tries to force air from the lungs with the vocal cords held closed (Valsalva maneuver).

The natural history of a venous malformation is slow, steady enlargement. Venous malformations generally grow as your child grows. However, events such as surgery, trauma, infection, or hormonal changes associated with puberty, pregnancy, or menopause may cause rapid expansion. They also can expand as a result of clot formation within the lesion. Large venous malformations or multiple venous malformations can be associated with clotting abnormalities. A venous malformation within the brain or gastrointestinal tract (stomach and intestines) can suddenly bleed.

Because there is wide variation in the presentation of these lesions, treatment varies. It depends upon the depth, location, and extent of the lesion. Treatment for symptomatic venous malformations or those in a critical location should be performed by a vascular anomalies specialist. Approaches used include the following:

• Observation. Small lesions that cause minimal cosmetic or functional upset are often observed over time without treatment.
• Compression garments. These are often used to control swelling and pain in extremity lesions.
• Sclerotherapy. This approach entails injecting an irritating solution into the lesion in order to shrink the abnormal veins. For larger lesions, it is sometimes used along with surgical excision. Multiple treatments are often required over time. Complications can include infection, localized tissue loss, and deep tissue scarring of the skin.
• Laser therapy. The skin component of a venous malformation, consisting of small vessels, is sometimes treated with a Nd:YAG laser or a KTP laser. Generally, several treatments six to eight weeks apart are necessary. Immediately after treatment there is considerable swelling, but this resolves with little or no pain within 5 to 6 days. Although laser therapy is effective in some patients, it may result in significant scarring. In other patients, this therapy may be ineffective.
• Surgical excision (removal). This approach is most successful when lesions are localized and accessible. Extensive lesions may, however, be only partially removable. Venous malformations are difficult to remove. Since they consist of a large number of dilated vessels with thin walls, they bleed more than other lesions during surgery. Extensive lesions may be only partially removable and it is sometimes necessary to sacrifice certain involved structures such as muscle and skin.
• Low Molecular Weight Heparin (LMWH) is used for patients that have a localized intravascular coagulopathy. It is used before and after surgical and interventional radiologic procedures. In some patients it is also used to manage chronic pain. Patients taking LMWH need to be supervised by a speciality team, with a hematologist.

Associated conditions with venous malformations include:

• Conditions involving Glomovenous malformations. These are venous malformations that contain glomus cells in the walls of the abnormal vessels. Glomus cells are nerve cells that cause these malformations to be tense and not as compressible. These lesions can be inherited and often are multiple.
• Blue rubber bleb nevus syndrome is characterized by multiple rubbery blue lesions over the skin (trunk, limbs). Lesions also can be internal and are seen mostly in the gastrointestinal tract (stomach and intestines). They vary in size from small to relatively large and can cause severe gastrointestinal bleeding and abdominal pain. Treatment consists of a combination of endoscopic and surgical removal.
• Maffucci’s syndrome. This syndrome is the coexistence of venous malformations and multiple enchondromas (benign bony growths). The child appears normal at birth, but before puberty, a hard nodule (small, localized outgrowth) appears most commonly on a finger or toe. This is soon followed by other nodules that involve the extremities and limbs. Dilated veins and soft bluish tumors occur in the affected limbs and elsewhere, and fracture of one or more bones often follows a minor injury.Healing is slow and unsatisfactory, resulting in other deformities that increase throughout childhood. Malignant (cancerous) degeneration of masses of tumor growth can occur. Multiple cosmetic and reconstructive operations are necessary. Because of the risk of malignancy, ongoing radiographic (X-ray) assessment as well as biopsy of lesions that enlarge rapidly or cause symptoms is necessary.