Renal vein thrombosis is a blood clot that develops in the vein that drains blood from the kidney.

Clot in the renal vein; Occlusion - renal vein

Renal vein thrombosis is an uncommon disorder that may be caused by:

• Abdominal aortic aneurysm
• Clotting disorders
• Dehydration (mostly in infants)
• Estrogen use
• Nephrotic syndrome
• Pregnancy
• Scar formation with pressure on the renal vein
• Trauma (to the back or abdomen)
• Tumor

In adults, the most common cause is nephrotic syndrome. In infants, the most common cause is dehydration.

• Blood clot to the lung
• Bloody urine
• Decreased urine output
• Flank pain or low back pain

An examination may not reveal the specific problem, but may indicate nephrotic syndrome or other causes of renal vein thrombosis.

• Abdominal CT scan
• Abdominal MRI
• Abdominal ultrasound
• Duplex Doppler exam of the renal veins
• Urinalysis may show protein in the urine or red blood cells in the urine
• X-ray of the kidney veins (venography)

The treatment is focused on preventing new clot formations and reducing the risk of the clot traveling to other locations in the body (embolization).

You may get medications that prevent blood clotting (anticoagulants) to stop new clots from forming. Your doctor may recommend bedrest or limited activity for a brief period.

If severe acute renal failure develops, you may need dialysis, but it should be temporary.

Renal vein thrombosis usually gets better over time without permanently injuring the kidneys.

• Acute renal failure (especially if thrombosis occurs in a dehydrated child)
• Blood clot moves to the lungs (pulmonary embolism)
• Formation of new blood clots

Call your health care provider if you have symptoms of renal vein thrombosis.

If you have experienced renal vein thrombosis, call your health care provider if you develop decreased urine output, difficulty breathing, or other new symptoms.

There is no specific prevention for renal vein thrombosis in most people. Keeping enough fluids in the body to avoid dehydration may help reduce its risk.

In people who have had a kidney transplant, aspirin is sometimes used to prevent renal vein thrombosis. In people with certain chronic kidney diseases, blood thinners such as warfarin may be recommended.

DuBose TD Jr, Santos RM. Vascular disorders of the kidney. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 126.

Kanso AA, Hassan NMA, Badr KF. Microvascular and macrovascular diseases of the kidney. In: Brenner BM, ed. Brenner and Rector's The Kidney. 8th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 32.