: Intravascular administration of iodinated contrast media is an essential tool for the imaging of blood vessels and cardiac chambers, as well as for percutaneous coronary and structural interventions. Along with the spreading of diagnostic and interventional procedures, the increasing incidence of contrast-induced nephropathy (CIN) has become an important and prognostically relevant problem. CIN is thought to be largely dependent on oxidative damage, and is a considerable cause of renal failure, being associated with prolonged hospitalization and significant morbidity/mortality. The most effective treatment strategy of this serious complication remains prevention, and several preventive measures have been extensively investigated in the last few years.Preprocedural hydration is the best-known and mostly accepted strategy. The administration of sodium bicarbonate has controversial effects, and is likely to be ineffective when the infused dose is unable to achieve adequate urine alkalinization. Since alkaline pH suppresses the production of free radicals, increasing urine pH would be an attractive goal for CIN prevention.In a prospective randomized controlled, open-label clinical trial we will test the hypothesis that urine alkalinization with either oral or intravenous bicarbonate on top of hydration alone is the main determinant of CIN prevention (primary endpoint) in a population of patients with moderate or severe chronic kidney disease scheduled for coronary angiography and/or angioplasty. If we then demonstrate nonsignificant differences in urine alkalinization and incidence of CIN between the two bicarbonate groups (secondary endpoint), a practical implication will be that oral administration is preferable for practical reasons over the administration of intravenous bicarbonate.