Reviewed by Brian R. Robinson, MDIn this condition, a blood clot forms in the renal vein, the vein that drains blood from the kidneys. Renal Vein Thrombosis is a rare condition that can occur for a variety of reasons. Causes include injury to the back or abdomen or from tumor or scar formation that lead to blockage of the vein, or from nephrotic syndrome, a condition marked by very high levels of protein in the urine resulting from damage to the kidneys’ blood filtering apparatus. In infants, this condition can result from dehydration.