Leg swelling has many causes; the most common vascular ones are chronic venous insufficiency, varicose veins and deep vein thrombosis. Sudden swelling of one leg with pain needs an urgent Doppler scan to rule out a clot. Chronic swelling of both legs at the end of the day is usually venous and improves with treatment and compression.
Swollen feet and ankles are among the most common complaints, especially in hot weather or after long hours on your feet. Most of the time it is mild and settles with rest, but sometimes it signals a blood-vessel problem that needs diagnosis and treatment.
Vascular causes of swelling
- Chronic venous insufficiency and varicose veins: when vein valves weaken, blood pools in the leg and fluid leaks into the tissues, so swelling appears late in the day and eases overnight. Read more about varicose veins and their treatment.
- Deep vein thrombosis: causes sudden swelling, usually of one leg, with calf pain, tightness and warmth. It needs prompt diagnosis. See deep vein thrombosis.
- After an old clot: some patients develop chronic swelling and skin changes after a previous clot that was not well followed up.
- Lymphoedema: swelling from poor lymphatic drainage, which can involve the foot and its upper surface.
Non-vascular causes to rule out
Not all swelling comes from the vessels. It can be due to heart failure, kidney or liver disease, low protein, or a side effect of some blood-pressure, diabetes and pain medicines. That is why assessment always starts with history and examination, then the right tests.
How to tell the types apart
- One leg or both? One-sided swelling points to a local cause such as a clot or venous insufficiency in that leg; swelling of both legs may have a general cause.
- Sudden or gradual? Sudden painful swelling needs same-day assessment.
- Better with rest and elevation? Clear improvement overnight suggests venous insufficiency.
- Skin changes? Brown discolouration or hardening near the ankle indicates chronic venous disease.
How is it diagnosed?
The key test for a vascular cause is a colour Doppler ultrasound of the leg veins. It shows a clot or venous reflux within minutes, painlessly and without radiation. Blood tests for heart, kidney and liver function may be added if both legs are swollen.
Treatment
Treatment depends on the cause. Venous insufficiency is treated with compression stockings and, when needed, by closing the faulty vein with laser or radiofrequency. A clot is treated with anticoagulants, and in selected cases with catheter techniques. Non-vascular causes are managed with the relevant specialty.
Tips that reduce swelling
- Raise your legs above heart level for 15 minutes several times a day.
- Move every hour if your work involves long sitting or standing.
- Cut down on salt.
- Ask your doctor before using compression stockings if you have diabetes or weak arteries.
Frequently asked questions
When is foot swelling serious?
When it is sudden in one leg with pain and warmth, or comes with shortness of breath or chest pain. These need a doctor immediately.
Do varicose veins cause swollen feet?
Yes. Venous insufficiency and varicose veins are a leading cause of swelling that worsens through the day and eases overnight.
What test is needed for a swollen leg?
A colour venous Doppler is the main test to rule out a clot and assess venous insufficiency, plus blood tests as needed.
Content on this website is for awareness only and does not replace a specialist medical examination.