Renal Vein Thrombosis

Renal vein thrombosis (RVT) is a clot in a main renal vein or one of its tributaries. The clot obstructs venous outflow, so blood and pressure build up within the kidney. That congestion can reduce filtration, produce hematuria and proteinuria, and, when both renal veins are affected, cause a rapid decline in kidney function. RVT is rare. In adults, the pattern most often points to nephrotic syndrome, active malignancy, renal-vein compression, or a primary hypercoagulable disorder. Nephrotic syndrome is particularly thrombogenic: urinary loss of antithrombin and other anticoagulant proteins removes natural brakes on coagulation, while the liver increases production of fibrinogen and other clotting factors. Reduced fibrinolysis and hemoconcentration add to the tendency to clot. The clot may be unilateral or bilateral. Bilateral involvement, thrombosis in a solitary functioning kidney, or extension into the inferior vena cava creates a much higher risk of acute kidney injury and systemic embolization. The left renal vein is affected more often because it has a longer course and can be compressed by surrounding vascular structures. Acute RVT can cause sudden flank or abdominal pain,...