Renal Resistive Index as an early Predictor of Contrast Induced Nephropathy in Patients Undergoing Coronary Angiography

Background: Contrast induced acute kidney injury (CI-AKI) is a common and serious complication of contrast agents used in imaging studies. Clinical markers useful for early detection of CI-AKI and prediction of outcome are needed in order to speed diagnosis and implementation of renal protective measures. In septic shock, postoperative setting of cardiac surgery and TAVI subjects, an increased Doppler Renal Resistive Index (RRI) is a predictor of AKI. This study aims to test the hypothesis that Doppler-based renal resistive index would similarly predicts contrast induced acute kidney injury in patients undergoing cardiac catheterization. Methods: We enrolled 100 patients undergoing cardiac catheterization and at risk of CI-AKI. All presented with at least two CI- AKI risk factors and were free of other identifiable causes of acute kidney injury or arrhythmia. Doppler RRI was measured before and at first day after catheterization. CI-AKI was assessed, defined by serum creatinine increase 25% above the pre-procedural baseline or rise in serum creatinine of >0.5 mg/dl from baseline value or a >25% decrease in eGFR within 5 days after cardiac catheterization. Results: Nineteen subjects developed CI- AKI in the first five days post-procedure, with two requiring dialysis. Post procedural RRI value was higher in CI-AKI subjects [RRI: 0.77±0.02 with CI- AKI vs 0.67±0.03 without CI-AKI, (P <0.001)]. In addition, the RRI increased significantly in the first day after the procedure [from RRI 0.7±0.38 preprocedural to 0.77±0.02 in patients developing CI-AKI (p<0.001)]. Post procedural RRI >0.744 predicted CI- AKI with a sensitivity of 94% and specificity of 92%. Conclusion: Measurement of the Doppler-based RRI early post-catheterization in high risk patients enabled early prediction of contrast induced acute kidney injury.