Lower extremity deep vein thrombosis: general information

Deep vein thrombosis of the lower extremities [deep vein thrombosis (DVT) occurs when blood clots in the deep veins of a limb (usually the calf or thigh)] or pelvis. Deep vein thrombosis of the lower extremities is the leading cause of pulmonary embolism. Deep vein thrombosis of the lower extremities occurs in conditions that impair venous return, causing endothelial damage and dysfunction.

Deep vein thrombosis of the lower extremities may occur in the deep veins of the upper extremities (4-13% of cases of deep vein thrombosis), lower extremities, or pelvis. Deep vein thrombosis of the lower extremities is much more likely to cause pulmonary embolism (PE), possibly because the thrombus is larger. The superficial femoral and popliteal veins in the thigh and the posterior tibial vein in the calf are most commonly affected. Deep vein thrombosis of the calf veins is less likely to be the source of a large embolus, but may cause recurrent dissemination of small emboli or may extend to the proximal veins of the thigh and subsequently cause pulmonary embolism. About 50% of patients with deep vein thrombosis have asymptomatic pulmonary embolism, and about 20% of patients with pulmonary embolism have deep vein thrombosis of the lower extremities.

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Causes of deep vein thrombosis of the lower extremities

Many factors can contribute to deep vein thrombosis of the lower extremities. Deep vein thrombosis of the lower extremities most often results from decreased venous return (eg, in immobilized patients), endothelial damage, dysfunction (eg, after leg fractures), or hypercoagulability.

What causes deep vein thrombosis in the lower extremities?

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Symptoms of Deep Vein Thrombosis of the Lower Extremities

Most deep vein thromboses occur in the small veins of the leg and are asymptomatic. When symptoms do occur (eg, vague aching, tenderness along the vein, swelling, erythema), they are nonspecific, vary in frequency and severity, and are similar in the arms and legs. Visible or palpable dilation of the collateral superficial veins may be present. Calf discomfort elicited by flexing the ankle with the knee straight (Homans' sign) is sometimes detected in deep vein thrombosis of the distal leg, but it lacks sensitivity and specificity.

Deep Vein Thrombosis of the Lower Extremities: Symptoms

Diagnosis of deep vein thrombosis of the lower extremities

History and physical examination help to identify the possibility of deep vein thrombosis before performing investigations. The diagnosis is confirmed by Doppler ultrasonography with flow study (duplex ultrasonography). The need for additional studies (eg, D-dimer study), their choice and sequence depend on the results of the ultrasound. No existing protocol of the study is recognized as the best.

Deep Vein Thrombosis of the Lower Extremities: Diagnosis

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Treatment of deep vein thrombosis of the lower extremities

Treatment is aimed primarily at preventing pulmonary embolism, and secondarily at reducing symptoms, preventing chronic venous insufficiency and postphlebitic syndrome. Treatment of deep vein thrombosis of the lower and upper extremities is generally the same.

All patients are given anticoagulants, initially injectable heparin (unfractionated or low molecular weight), then warfarin (in the first 24-48 hours). Insufficient anticoagulant therapy in the first 24 hours may increase the risk of pulmonary embolism. Acute deep vein thrombosis can be treated on an outpatient basis if there is no suspicion of pulmonary embolism, severe symptoms (in which case parenteral analgesics are indicated), other nuances that prevent safe outpatient treatment, and some specific factors (e.g., dysfunction, socioeconomic aspect).

Deep Vein Thrombosis of the Lower Extremities: Treatment

Prevention of deep vein thrombosis of the lower extremities

Patients at low risk for deep vein thrombosis (eg, those who have had minor surgery but have no clinical risk factors for deep vein thrombosis; or those who must be temporarily restrained for an extended period, such as during an airplane flight) should walk or perform intermittent leg movements. Flexing the legs 10 times per hour appears to be sufficient. No treatment is necessary.

How to prevent deep vein thrombosis of the lower extremities?

Prognosis of deep vein thrombosis of the lower extremities

Untreated deep vein thrombosis of the lower extremity has a 3% risk of fatal pulmonary embolism. Death due to deep vein thrombosis of the upper extremity is very rare. The risk of recurrent deep vein thrombosis is lowest in patients with transient risk factors (eg, surgery, trauma, temporary immobility) and highest in patients with permanent risk factors (eg, heart failure, malignancy), idiopathic deep vein thrombosis, or incomplete resolution of previous deep vein thrombosis (residual thrombus). A D-dimer level <250 ng/mL after stopping warfarin may help predict a relatively low risk of recurrent deep vein thrombosis or pulmonary embolism. The risk of venous insufficiency cannot be predicted. Risk factors for postphlebitic syndrome include proximal thrombosis, recurrent deep vein thrombosis on one side, overweight (BMI 22-30 kg/m2), and obesity (BMI > 30 kg/m2).