The Role of Renal Resistive Index (RI) in Predicting Acute Kidney Injury Progression in Intensive Care Clinic

Acute kidney injury(AKI) is defined in the KDIGO guidelines as a ≥0.3 mg/dL (≥26.5 micromol/L) increase in serum creatinine in the previous 48 hours or a ≥1.5-fold increase in serum creatinine from baseline, known or presumed to have occurred in the previous seven days, or a urine volume \<0.5 mL/kg/hour for six hours. Given the high morbidity and mortality associated with AKI, many investigators are studying several novel biomarkers to detect AKI progression earlier, identify etiologies and predict outcomes. However, the utilisation of these novel biomarkers may be constrained by reimbursement considerations. The renal resistive index (RRI) is a well-established metric for evaluating renal perfusion; however, its application in the context of AKI has been a subject of recent debate. While RRI has been utilised to demonstrate perfusion in acute and chronic renal diseases, particularly in conjunction with ultrasonography, its efficacy remains a subject of scientific discourse. In addition, Boddi reported that RRI is a strong indicator of mortality and a diagnostic marker, especially in patients with persistent AKI. The present study aims to evaluate the appropriateness of using the RRI, a non-invasive procedure, to determine the progression of AKI stages and the need for renal replacement therapy in patients hospitalised in intensive care units.