Sclerotherapy is a radiologically controlled, minimally invasive therapeutic procedure for the obliteration of venous malformations. Some sclerosing substances are also used to treat macrocystic lymphatic malformations. It is important to know that the actual “sclerosing” (obliteration) does not occur immediately, but is only fully completed weeks to months after local inflammation of the venous or lymph vessel wall with subsequent scarring.

Sclerotherapy does not eliminate the vascular malformation itself, but it usually leads to a reduction in the size of the lesion, significant alleviation of the discomfort and a reduction of risks caused by the vascular malformation. Compared to open surgery, sclerotherapy is much gentler on the surrounding tissue.

Sclerotherapy is generally performed under local anesthesia and analgosedation. In the case of sclerotherapy of the extremities, it is recommended that a tourniquet be applied during the procedure to facilitate puncture and prevent unwanted flow of sclerosing agent into the draining venous system. The vascular malformation is first punctured percutaneously by ultrasound using a needle. Depending on the size and configuration of the malformation, several punctures are often required during one treatment session.

After placement of the needle, the vascular malformation is visualized with an X-ray contrast medium (e.g., varicography). After radiographic confirmation of the correct needle position within the vessel malformation, estimation of the injection volume and exclusion of large draining vessels, the sclerosing agent is injected via the same needle. If large draining veins are visible, they should be closed before injection of the sclerosing agent. After removal of the puncture needles, a compression bandage is applied. This is important in order to allow close contact of the vein wall with the sclerosing agent and thus increase efficiency.

Sclerosing agents

The different sclerosing agents have very different effectiveness and side effect profiles, as described in the following section.

Ethanol (alcohol)/ethanol gel

Pure ethanol is one of the most effective sclerosing agents in the treatment of venous malformations. The sclerosing effect is based on massive damage to the endothelium with subsequent thrombosis. However, it is relatively common for the good sclerosing effect of alcohol to be accompanied by considerable local and systemic side effects. It is not uncommon for severe skin necrosis or persistent nerve damage to occur during sclerotherapy with pure alcohol. If alcohol enters the pulmonary circulation in large quantities, it increases pulmonary arterial pressure and can even lead to fatal circulatory failure in rare cases. Furthermore, disturbances of the blood sugar level (hypoglycemia) and cardiac arrhythmia have also been observed. To reduce systemic and local side effects, alcohol can also be applied in gelled form. This gelled alcohol is more viscous and thus more difficult to flush out of the lesion, has a longer contact time with the lesion and potentially fewer systemic side effects.


The intralesional administration of polidocanol (concentration usually 3.0%) leads to damage to the endothelium with subsequent inflammation and obliteration. Polidocanol is mainly used in the interventional treatment of venous malformations. Before percutaneous injection into the vascular malformation, polidocanol is foamed by many users in order to increase the intensity of action and to better control the distribution. The side effects profile of polidocanol is much more favorable than that of pure ethanol. However, the sclerosing effect is also somewhat less than that of ethanol, which is why the treatments have to be repeated more often.

Sodium tetradecyl sulfate (STS)

Sodium tetradecyl sulfate (usually 3.0%) leads to inflammation after contact with the vein wall, followed by thrombosis and sclerotherapy. It is therefore used in the treatment of varicose veins as well as in the treatment of venous malformations. The effect and side effects profile is very similar to that of polidocanol.

OK-432 (picibanil)

OK-432 (picibanil) is mainly used in the treatment of macrocystic lymphatic malformations. OK-432 is a lyophilized powder of attenuated streptococcal strains. The injection produces a strong immune response with local inflammation of the cysts of the lymphatic malformation. As a consequence of the subsequent inflammatory remodeling processes, the lymphatic fluid can be better removed and the cysts decrease in size significantly. Starting a few hours after the injection, a strong desired local inflammatory reaction occurs, often accompanied by swelling (caution when using in the respiratory tract). Occasionally, fever with flu-like symptoms may occur after the injection of OK-432. The fever responds well to antipyretic medication.


Bleomycin is an antibiotic/chemotherapeutic agent from the group of glycopeptides. It is also used in the treatment of micro- and macrocystic lymphatic and venous malformations and is very effective. In comparison to other sclerosing agents, the inflammation and swelling is somewhat less pronounced. Lung damage and possible induction of tumors are very rare side effects. It may be combined with reversible electroporation.


Doxycycline is an antibiotic from the group of tetracyclines with sclerosing properties and a good side effects profile. It is mainly used in the treatment of macrocystic lymphatic malformations.

Side effects and complications

Early reactions like swelling, inflammation and moderate pain are expected reactions of the body to sclerotherapy. They are part of the principal mode of action (closure by induction of inflammation) and are even desirable to a certain extent. In the case of very superficial lesions with thin skin coverage, the skin may become inflamed as well, sometimes leading to the formation of blisters or wounds. For relief, the treated region should be cooled and, if possible, compressed (compression bandage) and elevated. The need for symptomatic pain therapy should be considered generously. Serious local and systemic complications are to be expected, especially after the application of pure ethanol (see above). To avoid deep vein thrombosis, prophylactic anticoagulation with low-molecular-weight heparins for 7–10 days is recommended, especially in the case of sclerotherapy of the lower extremity. Finally, the potential complications caused by iodine-containing X-ray contrast media (renal insufficiency, hyperthyroidism, contrast medium allergy) should also be considered.

It must be emphasized again that the relieving effect of sclerotherapy only occurs after weeks, after the initial inflammatory phase has subsided.