What is vein injection sclerotherapy?

Injection sclerotherapy is a treatment that intentionally damages the lining (endothelium) of veins by injecting a chemical into the vein and inducing a chemical phlebitis or inflammation. By doing this and then applying pressure the vein walls stick together. The compression applied after the injection is an essential part of the therapy.

Foam sclerotherapy is an evolution of earlier methods and uses a standard sclerosant and mixes it with air or carbon dioxide in various ratios to create a foam. This foam is then injected into the veins. By using STS as a foam rather than a liquid the effect is potentiated especially in larger veins.

Ultrasound guided foam sclerotherapy is a further development in which the foam injection is guided by ultrasound. The ultrasound probe is able to track the needle entering the vein and ensure the injection takes place in the appropriate place.

Which varicose veins are suitable for injection sclerotherapy treatment?

Deciding whether your veins are suitable for injection sclerotherapy requires experience, knowledge and practice with all modalities of treatment. It is also important to balance the potential risks and complications against any possible benefit.

Even if your veins are suitable for injection sclerotherapy, it is important that you have a frank discussion with your specialist about the potential benefits and limitations.. It is important to be clear from the beginning what will be possible and what will not be possible. In some patients with very minor thread veins, injections may leave skin pigmentation that is no real improvement on the actual veins themselves. In these circumstances treatment will not improve the appearance of the veins and the use of false tan and camouflage cosmetics may be the best way to hide the visible veins.

Before your vein injection sclerotherapy

Well fitting compression stockings are an important part of the post injection regime and you should be measured for these before the treatment session so they are available to put on immediately after your injections.

The technique of vein injection sclerotherapy

The veins that may benefit from injections are identified. For spider veins  a small amount of liquid sclerosant is injected into the visible veins usually at multiple sites. Many microinjections can be performed at a single sitting. Immediately after the injections the areas injected tended to become red and have a slightly inflamed appearance. This is not painless but the discomfort is minimal.

For larger veins, foam sclerotherapy may be preferred, and cotton pads or other padding may be applied to the injected areas before the stockings are used..

After the vein injection sclerotherapy

After your injections you should go for a short walk of approximately 15 minutes. After that time you can carry on normal daily activities. Try to avoid standing still for long periods. If you are on your feet it is better to keep walking and if sitting to keep your legs elevated.

If wearing bandages, your surgeon will advise how long this is required. Stockings should be worn at all times day and night. Most surgeons would advise 14 days of compression for significant size veins Advice on the exact compression regime will vary and there is debate amongst practitioners on the appropriate level of compression as well as its duration.

Ultrasound guided foam sclerotherapy (UGFS)

When the sclerosant gas mixture is injected into the veins it can be traced using an ultrasound scanner. Using ultrasound guides the foam and may maximise the effect of the of syringe with differing silicone contents can affect the stability of the foam.

UGFS certainly can be effective but its medium to long term results are not reliably known. For treatment of saphenous vein reflux at the groin level,in a trial comparing all the major treatments, foam sclerotherapy came out as the least effective treatment with a 15-20% initial failure rate

Possible complications of injection sclerotherapy

Sclerotherapy is not without potential complications. For the vast majority of patients sclerotherapy is very safe and most patients experience minimal discomfort, but it is not completely pain free and occasionally the thrombosed veins can be moderately uncomfortable. Following sclerotherapy for larger veins they become very hard and lumpy but this will gradually resolve and the veins disappear. Following microinjections the spider veins can initially look a little worse as congealed blood in the veins looks darker but this also will resolve. Over the first few weeks following the injection, any slight discomfort, hardness or tenderness at the injection site(s) should gradually subside. If there is excessive redness, swelling or tenderness, this means you should rest more, with the leg raised so that the heel is higher than the hip. If you are concerned see your surgeon.

Brown staining of the skin around the site of the injection and along the line of the treated vein is quite a common event. Most patients experience complete or near complete resolution but this can take up to 12 months after the injections.

A persistent hard “cord” in the line of the vein – this usually occurs after injecting bigger varicose veins and means a small amount of blood has clotted in the vein. It is not dangerous and will resolve.


This is a common complication but will resolve completely often within one to two weeks.


This is a rare complication. Allergy to sulphur containing antibiotics does not seem to present a risk of also having an allergy to STS.

Visual disturbance

This is a rare complication (about 1 in 100 or 1%) for patients undergoing foam sclerotherapy. Patients experience a sparkling appearance in their vision which resolves after about 15 minutes. One study reported this complication in up to 3% of patients.

Rare instances of transient stroke reported (Forlee MV et al 2006). This is thought to be due to the foam bubbles travelling in the blood vessels to the brain. This is more likely to happen in patients with an occult patent foramen ovale (PFO). An interesting study (Wright, 2010) examined how common PFO was in patients with significant truncal varicose veins. In the general population about 25-30% of patients are thought to have a PFO which doesn’t affect them in day to day life and they are usually unaware of its presence. In the study 58.8% of patients were found to have a PFO. In most patients undergoing foam sclerotherapy to major veins, foam bubbles can be seen travelling in the blood to the heart. For the majority of patients this does not appear to be a concern, but because of potential risks I prefer to reserve UGFS for patients without major junctional reflux and keep the volume injected to a minimum.

Slight blistering and occasionally ulceration of the skin at the injection site – this is rare but usually means the fluid has been injected around the vein rather than into the vein. It is much more likely to occur when using higher concentrations of sclerosant.

The injection may fail to obliterate the vein.

Deep venous thrombosis

Although the risk of this is low it does occasionally occur. It may be related to the volume of sclerosant, particularly foam, that is injected. Larger volumes of foam injected close to the deeper veins may present more risk.

Useful links

http://www.dermnetnz.org/dna.cosderm/sclero.html – NZ dermatological society site with information on injection sclerotherapy


http://www.hta.ac.uk/fullmono/mon1013.pdf – Extensive review on surgical treatment and comparison with sclerotherapy.