Abstract: A method and device for preventing contrast associated nephropathy are disclosed. When contrast solution is injected into the coronary artery of a patient, blood is prevented from flowing through the coronary sinus into the right atrium. The blood in the coronary sinus is bypassed to a filtration device which filters out the contrast solution from the blood and recirculates the blood back to the patient. Preferably, blood flow from the coronary sinus is blocked by a balloon catheter which includes a port distal of the balloon so that when the sinus is occluded, blood flows from the sinus into the central lumen of the catheter where it can be directed to the filtration device.