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

Renal vein thrombosis is a fairly uncommon situation that may happen after trauma to the abdomen or back, or it may occur due to:

• Scar formation
• Stricture
• Tumor

It may be associated with nephrotic syndrome.

In some children it occurs after severe dehydration, and is a more serious condition than in adults. Dehydration is the most common cause of renal vein thrombosis in infants.

• 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, or abdominal ultrasound may show obstruction of the renal vein
• Urinalysis may show large quantities of protein in the urine, or red blood cells in the urine
• X-ray of the kidney veins (venography) may show renal vein thrombosis.