Duplex Ultrasound for Varicose Veins: What It Is and What Your Results Mean

A duplex ultrasound scan is the gold standard investigation for diagnosing varicose veins and chronic venous disease. It is a painless, non-invasive test that uses high-frequency sound waves to examine both the structure of your veins and the direction of blood flow within them.

Unlike a standard ultrasound, a duplex ultrasound combines two technologies: B-mode ultrasound produces real-time images of your veins and surrounding tissues, while Doppler ultrasound measures the direction and speed of blood flow, allowing the vascular specialist to determine whether blood is flowing normally or leaking backwards (venous reflux). Together, these provide a detailed map of your venous system and identify the underlying cause of your symptoms.

Why Is a Duplex Ultrasound Scan Important?

Although varicose veins can often be seen on physical examination, the visible veins are not always the source of the problem. The underlying venous reflux may arise from the great saphenous vein, small saphenous vein, accessory veins or perforator veins, none of which can be accurately assessed by examination alone.

A duplex ultrasound scan allows your vascular specialist to confirm whether venous reflux is present, identify which vein or veins are affected, assess the severity and extent of reflux, evaluate the deep veins to ensure they are open and functioning normally, detect superficial vein thrombosis or deep vein thrombosis (DVT) if present, map the veins before treatment, and determine which treatment option is most appropriate.

Without a duplex ultrasound scan, treatment decisions may be inaccurate, incomplete or directed at the wrong veins, increasing the risk of persistent symptoms or recurrence.

What Happens During the Scan?

The scan is performed using a small handheld probe placed on the skin with ultrasound gel. The examination is painless and does not involve needles, radiation or injections. Because gravity is important in revealing abnormal blood flow, much of the examination is performed while you are standing.

During the scan, the sonographer or vascular specialist may gently compress your calf or ask you to perform simple breathing manoeuvres. These techniques temporarily increase blood flow, making it easier to identify leaking vein valves. Most scans take approximately 20 to 30 minutes, depending on the complexity of the venous disease.

Is the Scan Safe?

Yes. Duplex ultrasound is extremely safe and has been used in vascular medicine for decades. It uses sound waves rather than X-rays, so there is no exposure to ionising radiation. The examination is painless, non-invasive and suitable for virtually all patients, including pregnant women.

Does Everyone with Varicose Veins Need a Duplex Ultrasound?

Current international guidelines recommend a duplex ultrasound scan before planning treatment for symptomatic varicose veins. The scan ensures that treatment is directed at the underlying cause of venous reflux rather than simply the visible veins.

Patients with uncomplicated spider veins who have no symptoms may not always require a duplex ultrasound. However, if there are symptoms such as aching, heaviness, swelling, skin changes, recurrent superficial vein thrombosis or a venous leg ulcer, duplex ultrasound is considered an essential part of the assessment.

Understanding Your Ultrasound Scan Results

Many patients feel anxious when they receive their ultrasound report because it contains unfamiliar medical terms. The good news is that an abnormal ultrasound scan does not automatically mean you need treatment. Your vascular specialist will interpret the findings together with your symptoms, physical examination and overall health before making any recommendations.

The primary purpose of the scan is to identify venous reflux — the backward flow of blood caused by faulty vein valves. The scan answers several important questions: Is venous reflux present? Which veins are affected? How severe is the reflux? Are the deep veins healthy and open? Is there any evidence of a blood clot? Which treatment, if any, is most appropriate?

Common Terms You May See on Your Report

Great Saphenous Vein (GSV) Reflux: The great saphenous vein is the longest superficial vein in the leg and the most common source of varicose veins. If your report mentions GSV reflux, it means that the valves within this vein are allowing blood to flow backwards instead of towards the heart. This is one of the most common patterns of chronic venous disease and is frequently treated with minimally invasive procedures such as EVLA or RFA.

Small Saphenous Vein (SSV) Reflux: The small saphenous vein runs along the back of the calf. Reflux in this vein also causes varicose veins and symptoms, although it is less common than GSV reflux. Treatment principles are similar but require careful ultrasound mapping because the anatomy can vary between individuals.

Accessory Vein Reflux: Some patients have reflux involving accessory saphenous veins, which are normal anatomical variants that run alongside the main superficial veins. These veins can become an important source of recurrent or persistent varicose veins and may also require treatment.

Perforator Vein Incompetence: Perforator veins connect the superficial veins to the deep veins. Normally, blood flows only from the superficial veins into the deep veins. If the perforator valves become incompetent, blood can flow backwards into the superficial veins, increasing venous pressure. Significant perforator reflux is more commonly seen in advanced chronic venous disease, particularly in patients with skin changes or venous leg ulcers.

Normal Deep Veins: One of the most reassuring findings on an ultrasound report is that the deep veins are normal and patent. The deep veins carry approximately 90% of the blood returning from the leg. Ensuring they are open and functioning normally is essential before planning treatment of the superficial veins.

Does an Abnormal Scan Mean I Need Treatment?

Not necessarily. Many people have ultrasound evidence of venous reflux but experience few or no symptoms. Conversely, some patients have relatively limited reflux but significant symptoms that affect their quality of life.

Your vascular specialist considers several factors before recommending treatment, including your symptoms, how much the symptoms affect your daily life, the severity and location of venous reflux, skin changes or other complications, and your overall health and personal preferences. Treatment is recommended when it is likely to provide meaningful clinical benefit — not simply because an ultrasound abnormality is present.

Why Ultrasound-Guided Treatment Is More Successful

Modern varicose vein treatment is based on correcting the underlying source of venous reflux, rather than simply removing the visible veins. Two patients may have almost identical-looking varicose veins but completely different patterns of reflux on ultrasound. This is why the ultrasound findings are essential in selecting the most appropriate treatment and achieving durable long-term results.

Rather than focusing on the medical terminology in your report, discuss the findings with your vascular specialist. Understanding what the results mean — and how they relate to your symptoms — is the first step towards choosing the most appropriate treatment for your individual condition.