Is Foam Sclerotherapy Dangerous?

Patients considering foam sclerotherapy for their varicose veins quite reasonably want to know whether the treatment is safe. In consultations with my patients, some express concern that injecting a chemical into a vein sounds rather alarming, particularly if they have read isolated reports online about complications such as deep vein thrombosis or visual disturbances.

The short answer is that foam sclerotherapy is a well-established, minimally invasive treatment with an excellent safety record. It is recommended by the National Institute for Health and Care Excellence (NICE) as part of the standard pathway for treating varicose veins in the UK, and it has been used on hundreds of thousands of patients worldwide over the past two decades. Serious complications are genuinely rare.

That said, no medical procedure is entirely without risk, and I think patients deserve a straightforward explanation of what those risks actually are, how likely they are to happen, and what is done to keep them as low as possible.

What is foam sclerotherapy?

Before discussing safety, it helps to understand what the procedure involves. Foam sclerotherapy uses a medical sclerosant, most commonly polidocanol or sodium tetradecyl sulphate, which is mixed with a small amount of air or gas to form a foam consistency similar to shaving cream. Under ultrasound guidance, the foam is injected through a fine needle into the affected vein.

The foam coats the inside lining of the vein, causing it to seal shut. Over the following weeks and months, the body breaks down and reabsorbs the treated vein, and blood is naturally rerouted through deeper, healthier veins. There are no incisions, no general anaesthetic, and no stitches.

What does the evidence say about safety?

The NICE interventional procedures guidance on ultrasound-guided foam sclerotherapy concluded that the evidence on safety is adequate for the procedure to be used in routine NHS practice, provided patients are made aware of the small risks. That is a meaningful endorsement from the UK’s independent body for assessing healthcare evidence.

Large prospective studies back this up. A multicentre study published in the European Journal of Vascular and Endovascular Surgery followed 1,025 patients undergoing foam sclerotherapy and reported an overall complication rate of around 7 to 8 per cent, with the vast majority of these being minor and self-limiting. A separate review in the same field estimated the rate of deep vein thrombosis at approximately 0.6 per cent, with most of these being small distal clots that resolved without long-term consequence.

In other words, the great majority of patients have a smooth and uneventful recovery.

Common, minor side effects

Most of what patients experience after foam sclerotherapy is mild and short-lived. Patients I have treated sometimes experience:

• Bruising along the treated vein. This is common and usually settles within two to three weeks.
• A pulling or tight sensation along the treated vein. This occurs as the vein contracts and is part of the normal healing process. It can last several weeks but is rarely uncomfortable.
• Brown skin discolouration (hyperpigmentation). Some patients develop a brown shadow along the line of the treated vein. This is caused by iron pigment from blood breakdown products and usually fades over six to twelve months, although in a small number of patients a faint mark can persist for longer.
• Tender lumps along the treated vein. These are areas of trapped blood within the closed-off vein and can feel firm under the skin. They are not dangerous and gradually soften and disappear.
• Mild redness or inflammation around the injection site. This generally settles within a few days.

None of these side effects is dangerous, and none of them requires specific treatment. They are best understood as a normal part of the body’s response to the procedure rather than as complications.

Rare but more serious complications

This is the area patients tend to ask about most, and rightly so. The complications below are uncommon, but it is right that you understand them before going ahead with treatment.

Deep vein thrombosis (DVT)

A DVT is a blood clot that forms in the deep venous system of the leg. As I explain on our page on rare complications, the risk of DVT following foam sclerotherapy is approximately 0.4 per cent, which is actually lower than the historical risk associated with open varicose vein surgery. The best protection against DVT is early mobility, which is why I encourage my patients to walk regularly straight after treatment and return to normal activities as soon as possible. The Circulation Foundation, the UK vascular disease charity, also provides useful patient guidance on this.

For patients with additional risk factors, such as a previous DVT, a high BMI, recent chemotherapy, use of hormone replacement therapy, or the combined oral contraceptive pill, I usually recommend a short course of blood-thinning injections (low molecular weight heparin) for seven days after treatment as a precaution.

Visual disturbances and migraine-type headaches

A small number of patients experience brief visual disturbances such as flashing lights or blurred vision, or a migraine-type headache, in the minutes or hours following treatment. These symptoms are transient, usually lasting less than an hour, and they leave no lasting effect. They are thought to be related to small amounts of gas from the foam entering the circulation, particularly in patients who have a patent foramen ovale (a small opening between the chambers of the heart that is present in around a quarter of the population). No long-term neurological damage from foam sclerotherapy has been recorded.

Allergic reaction

True allergy to the sclerosant is rare and serious anaphylactic reactions have only been described as isolated case reports. Patients are always asked about previous reactions to medication before treatment.

Skin staining or, very rarely, skin ulceration

If foam tracks into a very superficial vein close to the skin, it can occasionally cause a small area of skin inflammation or, very rarely, an ulcer. This is uncommon when the procedure is performed carefully under ultrasound guidance by an experienced operator.

Who needs to take extra care?

Foam sclerotherapy is suitable for the great majority of people with varicose veins, but there are some situations where it is either not recommended or requires additional precautions. The procedure should generally be avoided in patients who:

• Have had a previous allergic reaction to the sclerosant
• Have an active DVT or recent history of venous thromboembolism
• Have a known right-to-left shunt in the heart (such as a symptomatic patent foramen ovale)
• Are immobile or unable to walk after the procedure
• Are pregnant

This is exactly why a thorough consultation, including a duplex ultrasound scan, is important before treatment. It allows me to identify any patient-specific factors that might change the plan.

How do we keep the risks as low as possible?

In my view, the safety of foam sclerotherapy depends less on the procedure itself, which is well-established, and more on the care and attention given to each individual patient. At Southwest Veins, the things that genuinely make a difference are:

• A proper assessment. Every patient receives a full duplex ultrasound scan so that I understand the anatomy of their veins before any treatment is offered.
• An experienced operator. I have been performing foam sclerotherapy since 2007 and have treated well over a thousand patients with varicose vein problems.
• Ultrasound guidance throughout. The foam is tracked in real time so that I can see exactly where it is going.
• Sensible volumes of foam. Sticking to the recommended maximum volume per session significantly reduces the small risk of foam reaching the circulation in any meaningful quantity.
• Encouraging early mobility. Walking immediately after the procedure and returning to normal activities quickly is one of the single best things a patient can do to keep their risk of DVT low.
• Structured follow-up. I personally review every patient at six weeks and again at six months, so that any concerns are picked up early.

Putting the risks in perspective

It is worth remembering that varicose veins themselves are not entirely benign. Left untreated, they can progress to cause skin damage, venous eczema, bleeding from the vein, and superficial thrombophlebitis. The NHS recognises these as legitimate reasons to seek treatment.

When patients ask me whether foam sclerotherapy is dangerous, I usually point out that we are comparing the risks of a treatment with a very strong safety profile against the risks of leaving a structural problem untreated indefinitely. For most patients with troublesome varicose veins, the balance is firmly in favour of treatment.

Discuss your concerns

If you have read about a particular complication and want to know how it might apply to you, or if you simply want to talk through whether foam sclerotherapy is the right option for your varicose veins, I would be very happy to see you for a free, no-obligation assessment. Appointments are available either in person at our Plymouth clinic or via video consultation, whichever is more convenient.

Book your free assessment online now, or contact us with any questions you may have about foam sclerotherapy and its safety.