Risk factors include the following: Smoking, which doubles the risk (in 20 to 30% of patients) Obesity Excess use of phenacetin Acquired cystic kidney disease in dialysis patients Exposure to certain radiopaque contrast agents, asbestos, cadmium, and leather tanning and petroleum products Some familial syndromes, particularly von Hippel-Lindau disease and tuberous sclerosis RCC can trigger thrombus formation in the renal vein, which occasionally propagates into the vena cava.