Sclerotherapy — Procedure Guide, Recovery & Risks | MyMedicPlus

Sclerotherapy is a minimally invasive procedure that treats abnormal superficial veins — varicose veins, reticular veins, and spider veins (telangiectasias) — by injecting a chemical sclerosant agent directly into the target vessel. The sclerosant damages the vein's inner endothelial lining, triggering thrombosis and fibrosis, which causes the vein to collapse, become fibrous, and gradually fade over weeks to months as it is absorbed by the body.

Two forms of sclerosant are used: liquid sclerotherapy (using the agent in its aqueous form, suitable for spider and reticular veins) and foam sclerotherapy (where the sclerosant is mixed with air or CO2 to create micro-foam, displacing blood from the vein and maximising contact with the endothelium — more effective for larger varicose veins). The most commonly used sclerosants are sodium tetradecyl sulphate (STS/Fibrovein) and polidocanol (Aethoxysklerol), both approved for phlebological use internationally.

Sclerotherapy is one of the most extensively studied vascular treatments, with clinical use since the 1930s. It is performed by dermatologists, vascular surgeons, and phlebologists in outpatient clinic settings without the need for anaesthesia, incisions, or hospital admission. Multiple treatment sessions are usually required to achieve optimal clearance of varicose and spider veins.

Sclerotherapy is indicated for patients with symptomatic or cosmetically troublesome superficial venous disease. It is suitable for spider veins (telangiectasias — fine red or blue vessels, CEAP class C1) on the legs, reticular veins (blue-green feeding vessels, 2–4 mm, CEAP C1), and uncomplicated varicose veins (CEAP C2) following assessment to exclude significant saphenous reflux requiring thermal ablation (EVLA/RFA) as first-line treatment.

Additional indications include venous malformations (low-flow vascular birthmarks), recurrent varicose veins after previous surgery (where anatomical distortion makes repeat surgery complex), haemorrhoidal injection sclerotherapy (using phenol in oil), and treatment of hydroceles in men.

Assessment before treatment includes duplex ultrasound to map saphenous reflux and deep venous anatomy. If great saphenous vein (GSV) or small saphenous vein (SSV) reflux is present, the saphenous trunk should be ablated first (by EVLA, RFA, or foam sclerotherapy of the trunk) before treating tributaries. Contraindications include deep vein thrombosis or phlebitis within 3 months, known thrombophilia without anticoagulation, severe peripheral arterial disease, allergy to sclerosants, pregnancy, and immobility.

The patient stands briefly to distend target veins, then lies supine (to reduce hydrostatic pressure and slow blood flow in target vessels, maximising sclerosant contact time). No anaesthesia is required for most sclerotherapy.

For foam sclerotherapy of varicose veins, duplex ultrasound is used in real time to guide needle placement and confirm sclerosant distribution within the target vein. The Tessari method is used to prepare foam: sclerosant is rapidly mixed between two syringes connected by a 3-way stopcock (typically 1:4 sclerosant-to-air ratio) until a stable micro-foam is formed. Foam concentration is typically 3% STS or 2–3% polidocanol for truncal varicose veins, lower concentrations (0.5–1%) for spider veins.

Fine 30-gauge needles are used for spider veins; 23–25 gauge for larger varicose veins. 0.1–0.5 mL is injected per spider vein site; 0.5–2 mL per varicose vein site. The maximum safe foam volume per session is typically limited to 10 mL to minimise systemic absorption risk. Immediate blanching of the treated vein confirms correct intravenous injection. Gentle compression is applied immediately and maintained with a compression stocking or bandage. Treatment sessions typically last 30–45 minutes and 2–5 sessions are required for comprehensive clearance, spaced 4–8 weeks apart to allow treated veins to be reabsorbed before retreating.

Sclerotherapy requires no post-procedure downtime; patients walk immediately after treatment and return home independently. Compression stockings or bandaging (class 2, 23–32 mmHg) are worn continuously for 1–2 weeks after spider vein treatment and for 2–4 weeks after varicose vein treatment to maintain vein compression, prevent recanalisation, and reduce bruising.

Walking for 30 minutes immediately post-procedure activates the calf muscle pump and helps clear residual sclerosant from the circulation. Long periods of standing still or sitting are avoided for 48–72 hours. Strenuous exercise (running, gym) is deferred for 48–72 hours to prevent excessive vasodilation. Hot baths, saunas, and direct sun exposure over treated areas are avoided for 2 weeks as heat causes vasodilation and may worsen bruising and hyperpigmentation.

Treated veins appear bruised and inflamed initially, then progressively fade over 6–12 weeks. Small trapped blood clots (thrombophlebitis) can form in treated varicose veins within 2–4 weeks; these are drained by a simple needle puncture (thrombectomy) to speed resolution and reduce pigmentation risk. Final cosmetic result is assessed at 3–6 months after the last treatment session.

Skin hyperpigmentation — brownish discolouration along treated vessels — is the most common significant side effect, affecting 15–20% of patients. It results from haemosiderin deposition from lysed red blood cells in the treated vein and typically fades over 6–12 months in the majority of patients, though it can be permanent in a minority.

Telangiectatic matting — development of new fine red vessel networks around treated areas — occurs in 5–15% of patients and may require additional treatment. It is more common in patients taking the contraceptive pill or oestrogen therapy.

Superficial thrombophlebitis (inflammation of a treated varicose vein) is expected and managed conservatively. Deep vein thrombosis is a rare but serious complication, occurring in less than 0.1% of liquid sclerotherapy and 0.5% of foam sclerotherapy; anticoagulation is required if confirmed. Anaphylaxis to sclerosants occurs in less than 0.01% of injections. Visual disturbances (transient visual obscuration, migraine-like phenomena) occur in 1–2% of foam sclerotherapy sessions due to micro-bubble passage through a patent foramen ovale; these are typically transient and self-resolving. Skin necrosis from intra-arterial injection or perivascular extravasation is extremely rare (less than 0.1%) and avoidable with careful technique.

Sclerotherapy achieves clearance of spider veins in 70–90% of patients by the end of a course of 2–4 treatment sessions, providing significant cosmetic improvement and, for symptomatic patients, relief of aching, heaviness, and night cramps. Foam sclerotherapy of varicose veins and saphenous trunks achieves anatomical occlusion in 60–80% of treated segments at 1 year — somewhat lower than thermal ablation methods (EVLA 90–95%) but comparable for smaller-diameter veins.

The procedure is performed without anaesthesia, incision, or hospital admission, making it uniquely convenient compared to surgical and thermal alternatives. It is cost-effective, with unit costs significantly lower than laser ablation or surgery, and multiple body areas can be treated in a single session.

For patients who have had previous varicose vein surgery with recurrence due to neovascularisation, sclerotherapy is often the treatment of choice where repeat surgery would be technically difficult and risky. Health-related quality-of-life scores (Aberdeen Varicose Vein Questionnaire, AVVQ) show clinically meaningful improvement following sclerotherapy compared to watchful waiting in the CLASS trial.