Contrast induced nephropathy is a rising cause of acute renal failure in all patients. A study published in JAMA 2004, show a superiority of a hydratation with sodium bicarbonate in comparison with the same volume hydratation with sodium bicarbonate. The investigators will try following the original protocol making 2 randomized groups of patients, with cancer diagnosis, >18 years old, with a GFR <60 and >30 ml/min/1,73m2 by MDRD formula and/or diabetic patients. In the group 1 the patients will receive a solution with 154 mEq/L of a sodium bicarbonate, 3 cc/Kg/h at 1 hour before the injection of contrast and 1 cc/Kg/h during and 6 hours before the injection. The primary end point will be the rise of 25% or more in creatinine or dialysis needed.