3. a group with short-term sodium bicarbonate: NaHCO3 166mEq/l (3ml/kg; patients with a body weight above 100kg 300ml) as a bolus 20 minutes before contrast; additionally ingestion of Nephrotrans® (500mg NaHCO3/capsule: 1 capsule/10kg) with 1-2 dl of San Pellegrino® non-sparkling mineral water at the start of the infusion. Ingestion of 500ml San Pellegrino® non-sparkling mineral water in the first 6 hours after contrast.