Background: contrast-induced acute kidney injury (CI-AKI) is defined as acute impairment of renal function after administration of intra vascular iodinated contrast media, and it is considered as the third leading cause of acute kidney injury in hospitalized patients. Objectives: This study aimed to evaluate the clinical significance of pre-procedural Doppler based renal arterial resistive index for the prediction of CI-AΚI in patients with coronary artery disease (CAD). Patients and Methods: one hundred patients undergoing cardiac catheterization at risk of CI-AΚI were studied. All patients presented with at least two CI-AΚI risk factors and were free of other identifiable causes of acute kidney injury or arrhythmia. Doppler RRI was measured before and the one day after catheterization. CI-AΚI was assessed and was defined by increase in serum creatinine by 25% above the pre-procedural baseline or rise in serum creatinine >0.5 mg/dl from baseline value or >25% decrease in e-GFR within 5 days after cardiac catheterization. Results: fifteen subjects were developed CI- AΚI within five days post-procedure. Post procedural RRI value was higher in CI-AΚI subjects [RRI: 0.76±0.0l with CI-AΚI patients vs. 0.6l±0.04 without CI-AΚI P<0.00l]. In addition, the RRI was increased significantly in the first day after the procedure in patients with CI-AΚI (p<0.00l). Post procedural RRI >0.744 predicted CI-AΚI with a sensitivity of 94% and specificity of 92%. Conclusions: measurement of the Doppler-based RRI before and early post-coronary catheterization in high-risk patients enabled early prediction of contrast induced acute kidney injury.