What is Deep Vein Thrombosis?

Deep vein thrombosis - DVT - is a blood clot forming in one of the deep veins of the body, almost always in the calf or thigh. It is commoner than most people realise, often silent, and genuinely dangerous for one reason: a piece of the clot can break off and travel to the lungs.

What is actually happening

• Blood in the deep leg veins normally flows steadily back to the heart, helped by moving leg muscles
• When flow slows, the vein wall is injured, or blood becomes more prone to clotting, a clot (thrombus) can form and block the vein
• The blocked leg swells and aches - that is the DVT itself
• The danger: if part of the clot breaks free, it travels up through the heart and lodges in the lungs - a pulmonary embolism (PE), which can be fatal within an hour

Why it matters more than it sounds

• DVT and PE together (venous thromboembolism) are among the commonest preventable causes of hospital death
• Many DVTs produce mild or no symptoms - the first sign can unfortunately be the embolism
• The good news: diagnosed early, DVT is very treatable with blood-thinning medicines

Who should know about DVT

Everyone - but especially anyone having surgery (particularly hip or knee), anyone on bed rest, pregnant and new mothers, people with cancer, those on estrogen pills, long-distance travellers, and anyone with a previous clot or a family history of clots.

One-line summary

DVT is a clot in a deep leg vein - worth treating with urgency not because of the leg, but because of where a piece of it can go: the lungs. Recognised early, it responds very well to blood thinners; ignored, it can kill.