Sclerotherapy is a procedure used to treat both varicose veins and spider veins, involving an injection to make the vessels disappear. The treatment intentionally initiates a controlled inflammatory process within the targeted veins, which often raises questions about the risk of blood clots. Understanding the mechanics of sclerotherapy helps to distinguish between a desired therapeutic outcome and a serious complication. The primary goal is to close off dysfunctional surface veins, involving a specific type of localized clotting. While the procedure is safe, there is a small risk of a more serious type of blood clot that requires immediate medical attention.
How Sclerotherapy Works
Sclerotherapy involves injecting a liquid or foam chemical, known as a sclerosant, directly into the problematic vein. Common sclerosants, such as polidocanol, interfere with the fat molecules on the inner lining of the vein wall (endothelium), causing the endothelial cells to swell and become damaged. This damage triggers a cascade of reactions that cause the vein walls to stick together and seal shut. Once the vein is closed, blood flow is naturally rerouted to healthier veins nearby. Over time, the body treats the collapsed vein as scar tissue, which is then gradually broken down and absorbed.
The Expected Formation of Superficial Clots
The intended result of sclerotherapy is the creation of a thrombus, or clot, within the treated vein to seal it off. This localized clotting and inflammation is sometimes referred to as superficial thrombophlebitis (STP), representing the body’s expected reaction to the sclerosant and a necessary part of healing. Symptoms often include localized tenderness, firmness, redness, and a lumpy sensation along the path of the treated vessel. This discomfort is self-limiting and confined to the superficial venous system, meaning it is not dangerous, and usually resolves completely over several weeks or months. If the trapped blood (coagulum) is large and causing significant discomfort, a healthcare provider may drain it to hasten resolution.
Serious Risk Deep Vein Thrombosis
A more serious, though rare, complication is the formation of a Deep Vein Thrombosis (DVT), a blood clot that develops in the deep veins of the leg. Unlike the desired superficial clot, a DVT is concerning because it can break loose and travel through the bloodstream to the lungs, causing a potentially fatal pulmonary embolism. The risk of a symptomatic DVT following sclerotherapy is very low, estimated to occur in less than 1% of procedures. Symptoms demanding immediate medical attention include sudden, significant swelling in the entire limb, severe pain or a throbbing sensation in the calf or thigh, warmth, and discoloration of the skin. The primary mechanism for DVT development is often related to venous stasis (sluggish blood flow), which is exacerbated if the sclerosant inadvertently reaches the deep venous system; patients experiencing trouble breathing, chest pain, or dizziness should seek emergency care for potential pulmonary embolism.
Reducing Risk and Monitoring Recovery
Patient compliance with post-procedure instructions is the most effective strategy for minimizing the risk of all types of clots. Immediate and continued ambulation, such as walking, is strongly encouraged right after the procedure to promote healthy blood circulation and empty the deep leg veins, reducing the possibility of a thromboembolic event. Mandatory use of medical-grade compression stockings is also a standard protocol after sclerotherapy. The sustained pressure from the stockings helps keep the treated veins collapsed and assists in rerouting blood flow, mitigating the risk of a clot spreading. Patients should also maintain adequate hydration, avoid prolonged periods of sitting or standing without movement, and follow up with the treating physician if concerning symptoms arise for timely ultrasound evaluation.