![]() Muscle contractions and circulating plasminogen activators are constantly counteracting the formation of DVT. Lower extremity venous ultrasound is also used for postprocedural assessment of venous ablation and other interventions.ĭVT typically originates in the calf veins at valve sites where flow is slower and can propagate proximally into the veins of the thigh. Other indications include evaluation of venous insufficiency, reflux and varicosities, assessment for dialysis or other venous access, and venous mapping. Given its availability and low cost, venous ultrasound is also used for the follow-up of patients with known DVT and for determining residual thrombus load before ending anticoagulation therapy. The main indication for lower extremity venous ultrasound is the evaluation for possible venous thromboembolic (VTE) disease or venous obstruction in symptomatic or high-risk asymptomatic patients. The incidence for DVT has also been found to increase with age.Īntithrombin deficiencies (protein C and S)Įlevated levels of clotting factors (II, VII, VIII, IX, X, and XI)Įlevated plasminogen activator inhibitor–1 Additionally, demographic factors play a role, with the incidence higher in females than males, African Americans than whites, and lower in Asians and Native Americans. Hereditary or congenital conditions such as antithrombin deficiencies (protein C and S), factor V Leiden mutation, and antiphospholipid syndrome also predispose the patient to venous thrombosis. Acquired factors such as recent surgery or trauma, prolonged immobilization, pregnancy, oral contraceptive use, and underlying inflammatory states are the most common risk factors. Risk factors for DVT are summarized in Table 19.1. The pathophysiology of DVT was initially described by Virchow who observed that a combination of endothelial trauma, venous stasis, and hypercoagulability (Virchow triad) seemed to contribute to the development of DVT in most cases. ![]() Approximately 79% of patients with PE have evidence of DVT in their legs, and conversely up to half of patients with DVT may develop PE. Clots in the thigh veins can embolize to the lungs. Thrombi commonly form in the deep veins of the calf and propagate cephalad into the deep venous system of the thigh. It is estimated that approximately 900,000 cases of venous thromboembolism occur in the United States each year. The overall age- and sex-adjusted annual incidence has been estimated to be 48 cases per 100,000 individuals with the incidence relatively stable across age groups for males, decreased for women under 55 years of age, and increased for women older than 60 years. In patients with DVT, approximately 90% of cases involve the lower extremities and approximately 10% of cases occur in the upper extremities.
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