Background

Deep‐vein thrombosis (DVT) is a blood clot within the deep veins. It commonly occurs in the legs but can also form in the upper extremity, mesenteric, and cerebral veins. Similar to pulmonary embolism (PE), DVT is part of the venous thromboembolism (VTE) disorders.¹ Mortality from upper and lower extremity DVT occurs when a DVT breaks free and causes PE, which can lead to sudden cardiovascular collapse and other morbidity.

While a diagnosis of DVT is commonly considered in the ED when patients have leg swelling, calf pain, or other symptoms, they are often “silent” and are often diagnosed at autopsy. This makes the incidence of DVT difficult to estimate. The annual incidence of DVT has been estimated at 80 in 100,000 with a prevalence of leg DVT being significantly higher at 1 in 1000.^2,3 In the United States, greater than 200,000 people develop DVTs every year, with 1 in 4 cases also causing PE.⁴

Both DVT as well as PE are common and often “silent” and thus go undiagnosed or are only picked up at autopsy. Therefore, the incidence and prevalence are often underestimated. It is thought the annual incidence of DVT is 80 cases per 100,000, with a prevalence of lower limb DVT of 1 case per 1000 population. Annually in the United States, more than 200,000 people develop venous thrombosis; of those, 50,000 cases are complicated by PE. DVT is relatively rare in children and young adults; at the age of 40, the risk of DVT increases with age. Common conditions associated with DVT include cancer, heart failure, chronic obstructive pulmonary disease, and postsurgical patients.⁵

Accurate and timely identification of patients with DVT can minimize complications and morbidity. However, like PE, DVT is a relatively rare disease, which is often suspected but infrequently diagnosed. In the United States, approximately 1 in every 1000 ED visits results in the diagnosis of DVT.⁶ As with PE, the challenge in diagnosing DVT in the ED is the appropriate selection of patients for diagnostic testing and risk stratification based on clinical findings.

Venous noncompressibility on ultrasound is the major diagnostic criterion for DVT. Compression ultrasound, however, is not specific or sensitive for detecting DVT in patients with asymptomatic proximal DVT or in patients with DVT in the calf.⁷ It also demonstrates limited accuracy in cases of chronic DVT. The use of ultrasound is further limited in patients who are obese or who have edema.^8,9 However, despite these limitations, leg compression ultrasound is often used to detect DVT in the ED. Traditionally, only the proximal veins (from the femoral veins down to the calf, where they join the popliteal veins) are studied. While approximately 50% of DVTs begin in the calf,¹⁰ more than 70% of symptomatic DVTs involve the popliteal vein and more proximal leg veins.¹¹ In patients with calf DVTs that may not be detected on the first ED ultrasound, about 20% will extend more proximally within about a week. As DVTs that do not extend above the calf very rarely cause PE, proximal DVTs are at much higher risk for propagation and for causing PE.