DVT
Meaning of DVT: The leg symptoms are not the real danger; the danger is the fragment that breaks away and lodges in the lungs.
Definition of DVT
DVT stands for deep vein thrombosis, a blood clot forming inside one of the deep veins buried beneath the muscles, most often in the calf, thigh or pelvis. It may cause swelling, aching, warmth and a change in skin color on one side, or nothing noticeable at all. Clots in the superficial veins visible under the skin are a separate matter.
What makes a clot form?
| Contributing factor | Everyday examples |
|---|---|
| Blood moving slowly | Long immobility after surgery or illness, a cast on the lower limb, a long journey without moving |
| Damage to the vein wall | Surgery, fracture, a catheter sitting inside the vein |
| Blood that clots too readily | Cancer and its treatment, pregnancy and the weeks after birth, estrogen containing medicines, inherited clotting tendencies |
These three influences were described together long ago and still frame the subject. Most people who develop a clot have more than one of them at once, and the risk of any single factor rises sharply in company. A previous clot is itself among the strongest predictors of another.
What happens if part of it breaks free?
A fragment carried away in the bloodstream travels through the widening veins to the right side of the heart and then into the arteries of the lung, where the vessels narrow again and it wedges. That is a pulmonary embolism, and it is the reason a clot in the calf is taken seriously at all. It may cause sudden breathlessness, chest pain that worsens on breathing in, or a collapse, and a large one obstructs enough of the lung circulation to strain the heart severely. The two conditions are two presentations of a single process and are usually named together.
How is it confirmed, and what is left behind?
Physical signs are unreliable, since swelling and calf pain have many causes and a large share of clots produce little to notice. Ultrasound that presses on the vein to see whether it flattens is the standard test, supported by a blood test sensitive enough to rule the diagnosis out when it is negative but too unspecific to confirm it. Treatment thins the blood so the natural system can dissolve the blood clot without it growing. Even after successful treatment, damaged valves inside the vein leave some people with lasting swelling, aching and skin changes in that leg, a state called post-thrombotic syndrome.
Also known as
Used in a sentence
Ultrasound confirmed a DVT in the patient's left leg after several days of calf swelling.
Good to know
A DVT poses its greatest danger not through the leg symptoms it causes but through the risk that part of the clot travels to the lungs as a pulmonary embolism.