Balloon catheters for, and related methods of, preventing contrast-associated nephropathy are disclosed. A method for preventing contrast-associated nephropathy can include inserting a catheter into a patient's coronary sinus and blocking blood flow from the coronary sinus into the patient's right atrium. The blood may contain a contrast agent. The method can further include draining the blood from the coronary sinus through a first lumen defined by the catheter while the blood flow is blocked, filtering the contrast agent from the blood which passes through the catheter, and returning contrast-free or contrast-reduced blood to the right atrium through a second lumen defined by the catheter, which terminates in a port proximal to the coronary sinus. Another method can include selectively draining blood from the coronary sinus into the right atrium through a first lumen defined by a catheter that includes a switchable valve while the blood flow is blocked.
