Venous Doppler ultrasound for the assessment of varicose veins: what it involves and what information it provides

What is a venous Doppler ultrasound?

A venous Doppler ultrasound, also known as venous duplex ultrasound, combines two types of information.

Conventional ultrasound shows the anatomy of the veins: their course, their calibre and their relationship with neighbouring tissues. The Doppler system analyses the movement of the blood and allows the direction of blood flow to be assessed.

Thanks to this combination, the specialist can assess whether the veins are open, whether they compress normally and whether their valves allow blood to flow correctly back towards the heart. It is a non-invasive test. It uses ultrasound, does not involve ionising radiation and, when used to examine varicose veins, does not usually require contrast agents, needles, sedation or anaesthesia.

What is its purpose in the investigation of varicose veins?

In a person with varicose veins, Doppler ultrasound does more than simply show that there are dilated veins. Its main purpose is to determine why they have formed and the source of the increased pressure that keeps them dilated.

The veins in the legs contain valves that help blood flow towards the heart and prevent it from flowing backwards due to gravity. When one of these valves does not close properly, some of the blood may flow in the opposite direction. This phenomenon is known as venous reflux.

The scan makes it possible to locate the point where the reflux begins, trace its path and determine which superficial or deep veins are involved. It also helps to link the visible varicose branches to the vein that supplies them.

The National Institute for Health and Care Excellence (NICE), a UK body that produces healthcare recommendations based on the assessment of evidence, advises the use of Doppler ultrasound to confirm the diagnosis of varicose veins, determine the extent of reflux and plan treatment.

Why is simply looking at varicose veins not enough?

The external appearance of a varicose vein does not allow us to determine precisely which vein is malfunctioning, where the reflux begins, or how far it extends.

Two people with similar visible veins may have very different venous maps. In one person, the problem may stem from the great saphenous vein; in another, from a superficial branch, a perforating vein or changes related to previous treatment.

For this reason, the examination does not focus solely on the veins visible beneath the skin. The specialist systematically assesses the venous system and links the visible varicose veins to their possible origin.

Treating only the external branches without first assessing how the veins function may leave the underlying cause unaddressed or lead to treatment that is more extensive than necessary.

When is it usually requested?

A specialist may request a Doppler ultrasound when varicose veins are accompanied by a sensation of heaviness, pain, swelling, itching, cramps or discomfort that worsens when standing for long periods.

It is also usually recommended when there are changes in skin colour or hardening of the skin, venous eczema, an ulcer, inflammation of a superficial vein, bleeding from a varicose vein or a history of deep vein thrombosis.

The test is particularly useful before carrying out a treatment aimed at closing or removing a vein. In this context, it helps to confirm whether there is significant reflux, identify which segments are affected and plan a procedure tailored to each person’s anatomy.

It may also be requested when varicose veins recur after treatment or when there are concerns about the condition of the deep venous system.

Not all spider veins or all asymptomatic varicose veins automatically require a full assessment. Whether an assessment is indicated depends on the physical examination, medical history, symptoms and whether a procedure is being considered.

What can it detect?

Doppler ultrasound allows both the structure and function of the veins to be assessed. It can show whether there is reflux, where it originates and the path it follows. It also allows the saphenous veins, their branches, certain perforating veins and the deep venous system to be assessed.

During the scan, it is also checked whether the veins can be compressed normally and whether there are any signs of obstruction, recent thrombosis, sequelae of a previous clot or changes related to previous treatments.

In cases of recurrent varicose veins, the scan can help distinguish between a vein that has reopened, new varicose branches, or a site of reflux different from the one initially treated.

The report may include the diameter and depth of certain veins, as well as their relationship to visible branches. This information is useful for selecting and planning specific treatment techniques.

What can it not demonstrate or rule out on its own?

Doppler ultrasound provides detailed information about the veins examined, but does not, on its own, explain all leg symptoms.

Detecting reflux does not automatically prove that it is the cause of all symptoms, nor does it mean that treatment is necessary. The specialist must assess whether the finding is consistent with the physical examination, the distribution of the varicose veins, the condition of the skin and the patient’s medical history.

Similarly, a normal result does not rule out muscular, joint, neurological, arterial or lymphatic causes of pain, cramps or swelling.

The quality of the examination may be affected by severe oedema, obesity, wounds, dressings, severe pain, scarring, individual anatomy or difficulty in adopting the correct position. It also depends on the practitioner’s experience and the correct performance of the manoeuvres.

Is this the same test that is used to rule out thrombosis?

Not exactly. Both scans use the same technology, but they address different clinical questions.

The Doppler ultrasound requested in the event of a suspected deep vein thrombosis focuses primarily on looking for a clot and checking whether the deep veins are open and compressing correctly.

The scan for venous insufficiency or varicose veins in the legs also analyses how the valves are functioning. It examines the superficial system in greater detail and uses manoeuvres that temporarily alter the blood flow to check whether the blood is flowing backwards.

Consequently, an ultrasound scan carried out solely to rule out thrombosis may not include the reflux map required to plan treatment for varicose veins.

Differences from other venous tests

– Doppler ultrasound for reflux and Doppler ultrasound for thrombosis

The reflux study looks for abnormalities in valve function and is usually carried out with the leg bearing weight or in a position that promotes venous filling.

A thrombosis scan focuses on checking whether the deep veins are clear and can be compressed. It may include an analysis of blood flow, but it does not always examine all the superficial veins in detail, nor does it produce a map intended for treatment planning.

– Doppler ultrasound and phlebography

Phlebography uses a contrast agent administered via a vein and X-rays to visualise the venous system. It is an invasive technique that is currently reserved for specific situations, particularly when complex blockages are suspected or certain procedures are being planned.

For the routine assessment of varicose veins in the legs, Doppler ultrasound is usually the first test, as it allows the anatomy and function of the veins to be assessed without the use of contrast medium or radiation.

– Doppler ultrasound and CT angiography or MRI angiography

Computed tomography (CT) and magnetic resonance imaging (MRI) can provide information about veins in the pelvis or abdomen that are not always clearly visible on an ultrasound scan of the legs.

They do not routinely replace Doppler ultrasound in the investigation of superficial varicose veins. They may be considered when symptoms or findings suggest a higher-up venous obstruction, a malformation or a problem outside the area accessible to ultrasound.

How to prepare

In most cases, a venous Doppler ultrasound of the legs does not require fasting or any changes to your medication. You may eat and drink as normal, unless the clinic specifies otherwise due to specific circumstances. You should not stop taking anticoagulants, diuretics or other treatments on your own initiative.

It is advisable to wear clothing that is easy to remove, to avoid very tight-fitting garments and not to apply creams or oils to your legs before the test. It may also be helpful to bring reports of previous venous procedures and previous tests, if available.

The healthcare professional will need access to the limb from the groin to the ankle. Underwear may be kept on during the examination, and measures will be taken to ensure your privacy.

It is important to inform the healthcare professional if you have difficulty standing, severe pain, wounds, dressings or reduced mobility. Specific instructions from the Varicose Vein Unit take precedence over these general recommendations.

How it is carried out

The examination usually begins with a brief review of the reason for the appointment, your medical history and any previous venous treatments. The specialist may examine your legs whilst you are standing to identify the distribution of varicose veins, swelling or changes in the skin.

They then apply a water-based gel to the leg and move a small probe along the course of the veins. The images appear in real time on the monitor.

During the examination, the practitioner may gently press the vein with the probe to check whether it collapses. They may also compress the calf or foot to push the blood along and observe what happens when the pressure is released. At times, they may ask the patient to hold their breath and strain for a few seconds. This manoeuvre helps to assess the function of certain valves.

The probe systematically scans the main superficial and deep veins. When an abnormality is detected, its location, extent and relationship to visible varicose branches are recorded.

Why is part of the examination carried out whilst standing?

Veins fill differently when a person is lying down and when they are bearing their body weight. The upright position increases the effect of gravity and makes it easier to detect reflux that might be less obvious in a horizontal position. For this reason, the varicose vein examination is carried out whilst standing whenever possible and safe to do so.

If a person is unable to stand upright, the examination can be adapted using an inclined table or a seated position with the legs lowered.

How long does it take?

The duration depends on whether one or both legs are being examined, the complexity of the venous system, and whether any previous procedures have been carried out.

As a guide, the examination can take between 30 and 60 minutes. A bilateral examination, recurrent varicose veins or a more complex anatomy may require more time. The total time spent at the centre may be longer if it includes a consultation, a full clinical examination or an explanation of possible treatment options.

A longer test does not necessarily mean that there is a more serious condition.

Does it cause pain or discomfort?

Doppler ultrasound is usually well tolerated and does not cause pain in most people.

You may notice the cold gel, the pressure of the probe or some discomfort when a sensitive, swollen or wound-prone area is being examined. You may also find it tiring to stand for part of the test.

During the scan, you may hear pulsating or whooshing sounds. These represent blood flow and are normal. Some people may feel dizzy whilst standing. If this happens, please let the staff know straight away so that the scan can continue in a safer position.

Is contrast, sedation or anaesthesia used?

Intravenous contrast is not usually used to examine varicose veins using Doppler ultrasound. Nor is sedation or anaesthesia required, as no instruments are inserted into the body and no incisions are made. The gel is applied only to the skin and is removed at the end of the procedure.

There are specific contrast agents for some types of ultrasound scan, but these are not part of the standard investigation for venous reflux in the legs.

Risks and possible complications

Venous Doppler ultrasound is a non-invasive test with a favourable safety profile. It does not use ionising radiation, does not cause any wounds and requires no recovery time.

Any discomfort is usually limited to pressure on a sore area, discomfort caused by the position, or possible dizziness from standing for a prolonged period.

Gentle compression of the veins forms part of a standardised examination. It does not cause thrombosis or dislodge clots.

Contraindications and precautions

There are no common contraindications relating to pregnancy, pacemakers, metal prostheses or implants, as the test uses ultrasound.

Certain situations may require the examination to be adapted. These include difficulty standing, a risk of falling, severe pain, reduced mobility, open wounds, dressings, marked oedema or scars from previous treatments.

These circumstances do not necessarily prevent the test from being carried out, but they may limit access to certain areas or make it necessary to adjust the patient’s position.

What happens afterwards

Once the test is complete, the gel is wiped off and the patient can get dressed. No rest or special monitoring is required. You can walk, drive, eat, drink and resume your usual activities straight away.

When the scan forms part of a vascular consultation, the specialist may explain the main findings during the same appointment. In other cases, a report is drawn up for review at a later date.

The fact that a finding is discussed during the examination does not mean that a course of treatment has already been decided. A definitive interpretation requires integrating the ultrasound findings with the patient’s symptoms and clinical examination.

Results: who analyses them and how they are interpreted

The report usually describes which veins have been examined, whether they remain open, and whether there is reflux, obstruction or any signs of thrombosis. It may also indicate where the reverse flow begins, which section is affected, the calibre of certain veins and their relationship with visible varicose branches. In some cases, a diagram or venous map is included.

Reflux times and diameters form part of the assessment, but should not be interpreted in isolation. A specific value does not, on its own, determine whether a person requires treatment. The specialist considers the results in conjunction with the symptoms, the physical examination, the condition of the skin, the patient’s medical history and the potential benefit of treatment.

What does a normal result mean?

A normal result indicates that, within the veins and segments assessed, no pathological reflux, significant obstruction or signs of thrombosis have been detected. This may mean that the symptoms do not have a demonstrable venous cause or that the visible veins are not due to an underlying condition requiring treatment.

However, a normal result does not rule out all causes of pain, tiredness, swelling or cramps in the legs. If symptoms persist, the healthcare professional may investigate other possible causes, such as muscular, joint, neurological, arterial or lymphatic problems.

What happens if reflux is detected?

Detecting reflux does not automatically mean that treatment is required. The specialist assesses which vein is affected, the extent of the problem and whether it explains the symptoms or the changes observed in the skin. They also take into account previous treatments, the condition of the deep venous system and the patient’s preferences.

When reflux is clinically significant, venous mapping allows a technique to be chosen that targets the specific affected segment, thereby avoiding treatments based solely on the external appearance of the leg.

Incidental findings

During the scan, images may appear that are not directly related to the initial reason for the examination. Cysts, lymph nodes, fluid collections, soft-tissue masses or arterial changes are sometimes observed. Venous Doppler ultrasound is not designed to characterise these fully.

If an unexpected finding is detected, the specialist may recommend a further ultrasound scan, a more specific imaging test or additional assessment. An incidental finding does not necessarily mean that there is a significant condition.

Doppler ultrasound during the treatment of varicose veins

Ultrasound is not only used for diagnosis. During certain procedures, it enables the vein to be localised, a needle or catheter to be guided, and its position to be checked before treatment is administered. It can be used as a guide for endovenous laser treatment, radiofrequency ablation, ultrasound-guided sclerotherapy and other selected techniques.

After a procedure, it can also be used to check that the treated vein has closed, to examine the deep venous system or to assess whether varicose veins have recurred.

The type and schedule of follow-up depend on the technique used, the findings and the centre’s protocol.

Who performs and interprets the test?

At the Publio Cordón Memorial Hospital, Doppler ultrasound for the investigation of varicose veins forms part of the assessment carried out by the Varicose Vein Unit, which is part of the Department of Angiology and Vascular Surgery. The specialist interprets the images and flow measurements alongside the patient’s symptoms, physical examination, medical history and previous treatments.

This integrated approach is essential because detecting a vein with reflux is not, on its own, sufficient to decide on an intervention. The aim is to understand the origin of the problem and assess whether treatment is likely to provide a reasonable clinical benefit.

In which unit is the test carried out?

At the Publio Cordón Memorial Hospital, the test is carried out within the Varicose Vein Unit, which manages venous disease from the initial clinical assessment right through to the selection of treatment when indicated. Doppler ultrasound forms part of this process because it enables the symptoms and physical examination to be linked to the anatomy and function of the venous system.

Thus, the test is not considered in isolation, but rather as part of the clinical and therapeutic assessment of varicose veins.

When to seek advice after the scan

A Doppler ultrasound does not usually cause any after-effects and, under normal circumstances, there is no need to contact the centre after the scan. If the scan was carried out due to pain, sudden swelling or suspected thrombosis, you should follow the instructions provided by the specialist.