Section 11. Kidney and Urinary Tract Disorders

Chapter 145. Blood Vessel Disorders of the Kidneys

Topics: Introduction | Blockage of the Renal Arteries | Atheroembolic Kidney Disease | Cortical Necrosis | Malignant Nephrosclerosis | Renal Vein Thrombosis

Renal Vein Thrombosis

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

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 oral contraceptive use, injury, or, rarely, thrombophlebitis migrans--a condition in which clotting occurs sequentially in different veins all over the body.

Symptoms and Diagnosis

Blockage of the renal vein is usually gradual (chronic) but may be sudden (acute). Depending on whether the onset is gradual or sudden, the disorder follows one of two patterns.

In adults, onset and progression are usually gradual and without symptoms, and the disorder goes undetected. An occasional clue to doctors is when a piece of clot breaks off and travels from the renal vein to the lungs (pulmonary embolism (see Section 4, Chapter 46)). This event causes sudden pain in the chest 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 and with symptoms, and the disorder is detected. 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, protein and blood in the urine, and retention of fluid and salt (sodium) causing tissue swelling (edema). Blood tests may indicate an abnormally high number of white blood cells and evidence of kidney failure.

An ultrasound shows an enlarged kidney if the blockage developed suddenly; it shows a shrunken kidney if the blockage developed gradually. Imaging tests, such as intravenous urography and radionuclide scanning, show poor kidney function. X-rays of the inferior vena cava or the renal vein (venography) may reveal the outline of the blockage, and Doppler ultrasound studies, which use sound waves, are often helpful. When additional information is needed, computed tomography (CT) or angiography of the renal arteries may be performed.

Prognosis and Treatment

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 cause 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.

The primary treatment is with anticoagulant drugs, which usually improve kidney function by preventing additional clot formation and can reduce the risk of pulmonary embolism. Using drugs that dissolve clots (thrombolytics) is a newer treatment that is still not routine. Rarely, surgery is performed to remove clots in the renal vein. A kidney is rarely removed and then only if other complications develop, such as high blood pressure.