Venous thrombosis is a condition in which a blood clot (thrombus) forms in a vein. This clot can limit blood flow through the vein, causing swelling and pain. Most commonly, venous thrombosis occurs in the “deep veins” in the legs, thighs, or pelvis (figure 1); this is called a deep vein thrombosis, or DVT.
DVT is the most common type of venous thrombosis. However, a thrombus can form anywhere in the venous system. If a part or all of the blood clot in the vein breaks off from the site where it is formed, it can travel through the venous system; this is called an embolus. If the embolus lodges in the lung, it is called pulmonary embolism (PE), a serious condition that leads to over 50,000 deaths a year in the United States. In most cases, PE is caused when part of a DVT breaks off and lodges in the lung. The term “venous thromboembolism” is sometimes used when discussing both DVT and PE.
This topic review discusses the risk factors, signs and symptoms, diagnostic process, and treatment of a deep vein thrombosis. The diagnosis and treatment of pulmonary embolisms are discussed separately.