Deep vein thrombosis is the formation of blood clots (thrombi) in the deep veins.
- Blood clots may form in veins if the vein is injured, a disorder causes the blood to clot, or something slows the return of blood to the heart.
- Blood clots may cause the leg or arm to swell.
- A blood clot can break loose and travel to the lungs, which is called a pulmonary embolism.
- Doppler ultrasonography and blood tests are used to detect deep vein thrombosis.
- Anticoagulants are given to prevent pulmonary embolism.
In medicine, deep vein thrombosis (also known as deep-vein thrombosis or deep venous thrombosis and usually abbreviated as DVT) is the formation of a blood clot (“thrombus”) in a deep vein. It is a form of thrombophlebitis (inflammation of a vein with clot formation).
Deep vein thrombosis commonly affects the leg veins (such as the femoral vein or the popliteal vein) or the deep veins of the pelvis. Occasionally the veins of the arm are affected (if spontaneous, this is known as Paget-Schrötter disease). A DVT can occur without symptoms, but in many cases the affected extremity will be painful, swollen, red, warm and the superficial veins may be engorged. The most serious complication of a DVT is that the clot could dislodge and travel to the lungs, which is called a pulmonary embolism (PE). DVT is a medical emergency, present in the lower extremity there is 3% chance of a PE killing the patient. A late complication of DVT is the post-phlebitic syndrome, which can manifest itself as edema, pain or discomfort and skin problems.
The risk of DVT and PE is greater in people : –
- over 40 years of age,
- who have had blood clots already,
- with a family history of blood clots,
- suffering from, or who have had treatment for, cancer,
- with certain blood diseases,
- being treated for heart failure and circulation problems,
- who have had recent surgery especially on the hips or knees;
- who have an inherited clotting tendency.
DVT is also more common in women who : –
- are pregnant,
- have recently had a baby,
- are taking the contraceptive pill, or,
- are on hormone replacement therapy (HRT).
All patients with clinically suspected venous thrombosis or pulmonary embolism must have appropriate diagnostic testing to confirm the diagnosis.
Clinical suspicion alone is notoriously treacherous, since symptoms and signs of venous thromboembolism are highly non-specific, and this applies equally to a first presentation and to suspected recurrences. Ultrasound imaging is now the first investigation of choice for proximal (popliteal or femoral) vein thrombosis, although venography retains a key role in cases of suspected calf vein thrombosis (where ultrasound is relatively insensitive) or recurrent disease. A negative ultrasound examination for calf symptoms should be followed by immediate venography or by repeated ultrasound testing during the following week to rule out extension of an undetected calf clot. A normal lung scan rules out suspected pulmonary embolism, while a `high-probability’ ventilation-perfusion lung scan is sufficient evidence to treat. Venous ultrasound imaging, spiral CT-scanning or pulmonary angiography may help to guide management in patients with a `non-diagnostic’ lung scan.
Deep leg vein thrombosis is a very strong indication for anticoagulant therapy because of the high risk of early extension and embolism, and of subsequent recurrence. The bleeding risk is highest soon after surgery. It is increased by old age, low body weight, female gender, or malignancy, although none of these is an absolute contraindication. Interruption of the vena cava (see below) is an alternative to anticoagulant therapy within 24-48 hours of major surgery, or when there is active bleeding. There is a need for extra care with laboratory control of standard heparin and warfarin therapy if the bleeding risk is high.
While it is difficult to be certain what the exact causes of travel-related DVT are, experts agree that lack of exercise or immobility are major underlying risks. They have also identified that people at increased risk of DVT/PE in general are those more likely to develop travel-related DVT/PE.
Suspected DVT or PE is based on the history and the symptoms and is confirmed by ultrasound scanning or by a special x-ray taken after injecting a dye (contrast medium) that is opaque to X-rays (a venogram).