deep vein thrombosis

deep vein thrombosis (DVT), formation of a blood clot in a vein that lies deep beneath the surface of the skin. Deep vein thrombosis (DVT) usually occurs in the lower leg, thigh, or pelvis, but it also may develop in the arm, brain, intestines, liver, or kidney.

DVT is a serious condition that can cause long-term illness, disability, and death. A dangerous complication of DVT is pulmonary embolism, which occurs when a piece of a blood clot breaks off, travels through blood vessels to the lungs, and forms a blockage, known as an embolism, that obstructs blood flow.

Risk factors

Risk of DVT is associated with factors that affect blood flow and blood clotting, such as injury to a vein caused by a fracture, severe muscle injury, or major surgery—especially of the lower body and legs. DVT may also be precipitated by reduced blood flow, which can occur in persons who are paralyzed, who have limited mobility, who sit for long periods of time (especially with the legs crossed), or who are bedridden because of illness, hospitalization, or a recent operation. Smoking, obesity, older age, and a family history of thrombosis (blood clot formation) or embolism are additional risk factors, as is having previously experienced DVT—the condition recurs in about one-third of individuals.

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Pregnant individuals are at increased risk for DVT, especially if they are on bed rest prior to delivery or are resting in bed post-birth for several days, which is necessary after a cesarean section. In fact, risk of DVT is increased fivefold in pregnant individuals; this is because a growing fetus presses on the veins in the pelvis, reducing blood flow to the legs. Pregnancy also causes blood to clot more easily, which helps prevent excessive bleeding during labour and delivery. Persons who have increased estrogen levels also have an elevated risk of developing DVT; increased estrogen levels may be caused by pregnancy, oral contraceptives, or hormone replacement therapy.

Patients who have chronic medical conditions are also more likely to develop DVT. Such conditions may include heart or lung disease or inflammatory bowel disease (Crohn disease or ulcerative colitis). Risk of developing DVT is increased among cancer patients, particularly those with cancer of the pancreas, stomach, brain, lungs, uterus, ovaries, or kidneys, as well as among patients with certain cancers of the blood, such as lymphoma or multiple myeloma. Some cancer treatments, especially chemotherapy and hormonal therapy, also increase the chances of developing DVT.

Symptoms, diagnosis, and treatment

About half of individuals who develop DVT have no symptoms. When symptoms are present, they can include swelling, pain, cramping, tenderness, and discoloration of the skin (red or purple) in the area of the body where the blood clot has formed. The skin over the affected area may also feel warmer than usual.

Quick diagnosis of DVT is essential. Diagnosis can be made using venous duplex ultrasound, a noninvasive technology that uses sound waves to visualize blood flow and possible blood clots in the veins. Other imaging tests may be used, including doppler ultrasound, computed tomography angiography (CTA), magnetic resonance imaging (MRI), or magnetic resonance venography (MRV). Blood tests may be used to assess levels of a substance called D-dimer, a protein fragment produced when a blood clot dissolves or breaks up. Elevated levels of D-dimer are indicative of a blood clotting disorder.

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Treatment for DVT is aimed at keeping blood clots from increasing in size and at preventing blood clots from breaking off and traveling to the lungs. Some patients benefit from elevating the legs regularly and from wearing graduated compression stockings, which relieve pain and swelling and promote circulation in the legs. DVT patients are often prescribed anticoagulant drugs, which help prevent blood clots and help keep blood clots from increasing in size or breaking apart. DVT patients may need to take anticoagulants for long periods of time and may require blood testing to monitor for hemorrhage, a side effect of anticoagulant therapy. Thrombolytic drugs (fibrinolytic drugs) may be used when anticoagulants are ineffective. Some clots must be removed surgically, via surgical thrombectomy.

Complications

DVT is associated with long-term complications, referred to as post-thrombotic syndrome (PTS; also known as postphlebitic syndrome); such complications occur in about 20 to 50 percent of persons who have had DVT. PTS results from damage to the valves and inner lining of the vein inflicted by DVT. This damage causes blood to pool, thereby increasing pressure in the veins. PTS symptoms include pain, swelling, and discoloration in the part of the body where DVT occurred. Skin sores are also common. In severe cases—in about 5 to 10 percent of DVT patients—skin scaling or venous stasis ulcers (wounds commonly found on the legs or ankles) may develop.

Prevention

Prevention of DVT is possible through smoking cessation, exercise, and maintenance of a healthy weight. Persons who have had surgery or who have been in bed because of illness or injury are encouraged to resume movement as soon as possible. Wearing loose-fitting clothing, moving at regular intervals, stretching, and contracting and relaxing muscles in the legs can help facilitate blood flow for individuals who must sit for long stretches of time. Pregnant individuals at high risk of blood clots may be prescribed heparin, an anticoagulant, to help prevent DVT.