The clot can damage the kidney.
Symptoms may be minimal unless the clot develops suddenly.
Diagnosis is with magnetic resonance angiography, Doppler ultrasonography, or computed tomography angiography.
Treatment may include anticoagulant drugs, clot-dissolving (fibrinolytic) drugs, and removal of the clot.
In adults, the most common cause of renal vein thrombosis is
In nephrotic syndrome, large amounts of protein are lost in the urine and the blood has an increased tendency to form clots.
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, into which the renal vein drains. Other possible causes are blood clotting disorders (hypercoagulability disorders), vasculitis, systemic lupus erythematosus (lupus), sickle cell disease or diabetes that affects the kidneys, oral contraceptive use, injury, cocaine abuse, or, rarely, thrombophlebitis migrans—a condition in which clotting occurs sequentially in different veins all over the body.
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). 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, nausea, vomiting, less than a normal amount of urine, and blood in the urine.
Blood tests may indicate evidence of a decrease in the ability of the kidneys to process and excrete the body's waste products (kidney failure). Routine urine testing is also done.
Magnetic resonance (MR) angiography, Doppler ultrasonography, and computed tomography (CT) angiography are the tests doctors use to diagnose renal vein thrombosis (see Imaging Tests of the Urinary Tract). MR angiography and CT angiography are highly accurate and do not require insertion of a catheter into an artery or a vein deep in the body. Ultrasonography is not as accurate, but it is very safe. Ultrasonography shows enlarged kidneys if the blockage developed suddenly. Doppler ultrasonography may show that there is no blood flowing in the renal vein. X-rays of the inferior vena cava or the renal vein that are taken after a radiopaque contrast agent 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.
The underlying disorder is treated. 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. Sometimes a catheter is inserted into the vein to give a drug that dissolves clots (fibrinolytic) or to remove the clot (called thrombectomy). These newer treatments are becoming more widespread but are 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.
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.