Deep vein thrombosis, or deep venous thrombosis (DVT), is the formation of a blood clot (thrombus) within a deep vein,[a] most commonly the legs. Nonspecific signs may include pain, swelling, redness, warmness, and engorged superficial veins. Pulmonary embolism, a potentially life-threatening complication, is caused by the detachment (embolization) of a clot that travels to the lungs. Together, DVT and pulmonary embolism constitute a single disease process known as venous thromboembolism. Post-thrombotic syndrome, another complication, significantly contributes to the health-care cost of DVT.
In 1856, German pathologist Rudolf Virchow postulated the interplay of three processes resulting in venous thrombosis, now known as Virchow’s triad: a decreased blood flow rate (venous stasis), increased tendency to clot (hypercoagulability), and changes to the blood vessel wall. DVT formation typically begins inside the valves of the calf veins, where the blood is relatively oxygen deprived, which activates certain biochemical pathways. Several medical conditions increase the risk for DVT, including cancer, trauma, and antiphospholipid syndrome. Other risk factors include older age, surgery, immobilization (as with bed rest, orthopedic casts, and sitting on long flights), combined oral contraceptives, pregnancy, the postnatal period, and genetic factors. Those genetic factors include deficiencies with antithrombin, protein C, and protein S, the mutation of factor V Leiden, and the property of having a non-O blood type.
Individuals suspected of having DVT may be assessed using a clinical prediction rule such as the Wells score. A D-dimer test may also be used to assist with excluding the diagnosis (because of its high sensitivity) or to signal a need for further testing. Diagnosis is most commonly done with ultrasound of the suspected veins.
Prevention options for at-risk individuals include early and frequent walking, calf exercises, anticoagulants, aspirin, graduated compression stockings, and intermittent pneumatic compression. Anticoagulation is the standard treatment; typical medications include low-molecular-weight heparin or a vitamin K antagonist. Wearing graduated compression stockings appears to reduce the risk of post-thrombotic syndrome. The rate of DVTs increases from childhood to old age; in adulthood, about one in 1000 adults is affected per year.