Patients with acute coronary syndromes (ACS) are at increased risk for acute kidney injury (AKI) when they undergo urgent/emergency coronary angiography. The optimal medical treatment for preventing the occurrence of contrast induced - acute kidney injury is still controversial. Fenoldopam mesylate is a dopamine A1 receptor agonist that augments renal plasma flow that has reduced the risk of radiocontrast dye nephropathy in some (but not all) preliminary studies. Neutrophil gelatinase-associated lipocalin (NGAL) is a new biomarker predictive for AKI already shown to be useful for earlier diagnosis of contrast induced nephropathy. The primary objective of this study is to to test the hypothesis that fenoldopam, in addition to standard treatment, reduce the occurrence of contrast induced - acute kidney injury in patients with acute coronary syndrome (ACS) undergoing urgent/emergency coronary angiography and/or percutaneous coronary intervention.