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Renal vein thrombosis is blockage of the renal vein, which carries blood away from the kidney, by a blood clot.

• The clot can damage the kidney or can break off, causing a piece of it to travel through the bloodstream (becoming an embolus).
• Symptoms may be minimal unless the clot develops suddenly.
• Diagnosis is with computed tomography angiography or magnetic resonance angiography.
• Treatment includes anticoagulant drugs and sometimes clot-dissolving (fibrinolytic) drugs.

In adults, renal vein thrombosis usually occurs with other kidney disorders that cause the nephrotic syndrome, in which large amounts of protein are lost in the urine. Renal vein thrombosis may also be caused by kidney cancer or conditions that put pressure on the renal vein (for example, a tumor) or on the inferior vena cava, which the renal vein drains into. Other possible causes are blood clotting disorders (hypercoagulability disorders), vasculitis, sickle cell disease or diabetes that affects the kidney, oral contraceptive use, injury, cocaine abuse, or, rarely, thrombophlebitis migrans—a condition in which clotting occurs sequentially in different veins all over the body.

Symptoms

Renal vein thrombosis occurs most often in adults. In adults, onset and progression are usually gradual and without symptoms. An occasional clue to doctors is when a piece of clot breaks off and travels from the renal vein to the lungs (pulmonary embolism—seePulmonary Embolism (PE): Pulmonary Embolism). This event causes sudden pain in the chest that is made worse by breathing, along with shortness of breath. In other people, urine production diminishes.

In most children and a limited number of adults, onset and progression are usually sudden. Pain, often the first symptom, typically occurs in the back behind the lower ribs and in the hips. The person may have fever, less than a normal amount of urine, and blood in the urine.

Diagnosis

Blood tests may indicate evidence of kidney failure.

Computed tomography (CT) angiography and magnetic resonance (MR) angiography are the tests doctors use to diagnose renal vein thrombosis. They are highly accurate and do not require insertion of a catheter into an artery or a vein deep in the body, so they are usually the preferred tests. Ultrasonography is not as accurate, but it is very safe. An ultrasound scan shows enlarged kidneys if the blockage developed suddenly. Doppler ultrasonography may show that there is no blood flowing in the kidney vein. X-rays of the inferior vena cava or the renal vein that are taken after a radiopaque dye is injected into an artery or deep vein (venography) is the most accurate test, but may cause clots to break off and travel through the bloodstream, becoming emboli, which can cause complications.

Prognosis

The outcome depends on the cause of the thrombosis, complications, and the degree of kidney damage. Death from renal vein thrombosis is rare and usually results from a fatal underlying disorder or from complications, such as a pulmonary embolism. The effects on kidney function depend on whether one or both kidneys are affected, whether blood flow is restored, and what the state of kidney function was before the blockage occurred.

Treatment

The primary treatment is with anticoagulant drugs, which usually improve kidney function by preventing the formation of additional clots and reducing the risk of pulmonary embolism. Use of drugs that dissolve clots (fibrinolytics) is a newer treatment that is becoming more widespread but is still not routine. Rarely, surgery is done to remove clots in the renal vein. A kidney is rarely removed and then only if other complications, such as high blood pressure, develop.