Contrast nephropathy (CN) remains a common complication of radiographic procedures and an important cause of hospital-acquired acute renal failure. Only hydration with saline is uniformly accepted and used in clinical practice as a cornerstone for the prevention of CN. But the optimal preventive strategy for CN is not known. Sodium bicarbonate might be even more effective than hydration with sodium chloride for prophylaxis of CN. Therefore the aim of the study is to evaluate the efficacy of two regimens of sodium bicarbonate compared with a prolonged infusion of sodium chloride in the prevention of CN.