Doppler Ultrasound Scan of the Legs examines the lower limbs for arterial blood flow – “circulation” – and venous thrombosis – “clots”.
Ultrasound works on the principle of reflection of high-frequency sound waves at interfaces between tissues of different density. It does not use any radiation and is safe for children and pregnant women.
Doppler ultrasound is a technology which shows blood flow as colour images based on the speed and direction of flow.
How the Test is Performed
Ultrasound scanning is performed by a specifically trained Sonographer, who uses the ultrasound machine to obtain images on a screen, usually in black and white. Colour-flow Doppler shows blood flow as blue or red spreading areas. These images are stored electronically and can be printed out for viewing, but most of the information is gained by an experienced sonographer during the actual examination.
A special probe is applied with mild to moderate pressure against the leg, over the areas where veins are found. A gel is used on the skin to form an acoustic interface with the probe. Pressure may be uncomfortable over tender areas.
The examination usually takes about half an hour, but may take more than an hour if arterial flow is being assessed.
Medical Conditions and Symptoms
Ultrasound Scan of the legs may be requested when a Deep Vein Thrombosis (DVT) – a clot in the deep veins of the leg – is suspected. Symptoms of a DVT include calf or leg pain and swelling of the calf or ankle.
Doppler Ultrasound is also capable of assessing arterial blood flow in the lower limbs, to look for areas of narrowing due to atherosclerosis or to assess the function of arterial grafts, in people with Peripheral Vascular Disease (PVD).
Test Results Explained
Ultrasound results are usually forwarded to your doctor for interpretation and explanation. The Sonographer may communicate some of the scan findings during the actual examination.
Clot in a vein will prevent flow being seen in that vessel, and will make the vein solid, being non-compressible with the ultrasound transducer.
Superficial veins are differentiated from deep veins – clot in superficial veins is usually not serious, but may progress to clotting in the deeper veins. The main danger with Deep Vein Thrombosis is that the clot may break off and travel up to the lungs blocking blood flow and oxygenation. This can be very serious and in the worst cases can be life-threatening. Treatment of DVT usually involves anticoagulation (thinning the blood with medication) whilst the clot dissolves.
Arterial assessment aims to determine the presence of narrowed blood vessels and does this by evaluating the speed and quality of flow within these vessels. The report will usually describe the severity of the stenosis (narrowing).
- General Practitioner (GP)
- Vascular Surgeon
- General Physician
- Medical Oncologist
- Respiratory Physician
- Orthopaedic Surgeon
- Carotid Doppler Ultrasound Scan
- CT Pulmonary Angiogram (CTPA)
- VQ Scan (Ventilation-Perfusion Scan)
- Echocardiogram (Echo)
- Electrocardiogram (ECG)
- INR Test (International Normalised Ratio)
Also Known As