Deep vein thrombosis
Also known as: DVT, blood clot in the leg
A blood clot in a deep vein, most often of the calf or thigh.
Overview
Clots form when blood flow slows, the vein wall is injured or the blood clots too easily (Virchow's triad). A leg DVT causes pain and swelling; its danger is that a fragment can break off and lodge in the lungs as a pulmonary embolism.
Causes
- Immobility: surgery, long flights, bed rest, plaster casts
- Cancer and chemotherapy
- Pregnancy, the combined pill and hormone replacement
- Inherited clotting tendencies (factor V Leiden and others)
- Injury to the vein
Risk factors
- Age
- Obesity
- Smoking
- Previous DVT
- Dehydration
Symptoms
What a clinician may find
- One calf swollen more than 3 cm larger than the other, warm, tender, with dilated surface veins
Complications
- Pulmonary embolism
- Post-thrombotic syndrome: chronic swelling, pain and skin ulcers
Diagnosis
A clinical probability score, a D-dimer blood test to rule out low-risk cases, and compression ultrasound of the leg veins to confirm.
Treatment
Anticoagulation for at least three months, usually with a direct oral anticoagulant (apixaban, rivaroxaban) or warfarin; compression stockings for symptoms; early mobilisation. Large clots occasionally need catheter-directed clot removal.
Prevention
Move early after surgery, use prescribed stockings and injections in hospital, walk and hydrate on long journeys, stop smoking.
When to seek care
Same-day assessment for a swollen painful calf; emergency care if breathlessness or chest pain develops.