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

Overview

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.

Acute kidney injury(AKI) KDIGO guidelines for AKI include an increase in serum creatinine of ≥0.3 mg/dL (≥26.5 micromol/L) in the last 48 hours or an increase in serum creatinine of ≥1 mg/dL (≥26.5 micromol/L) from baseline, known or presumed to have occurred in the previous seven days, 5-fold increase or urine volume \<0.5 mL/kg/hour for six hours. The incidence of in-hospital AKI varies between 7. 0-18.3% in hospitalized patients in general and up to 20-50% in critically ill patient populations . In addition to causing a high mortality and morbidity, especially in critically ill patients, AKI prolongs the duration of hospitalization in the intensive care unit. Due to the high morbidity and mortality associated with AKI, many researchers have been studying several novel biomarkers for earlier detection of AKI progression, identification of etiologies and prediction of outcomes. However, the use of these new biomarkers may be limited by reimbursement issues. Although renal resistive index(RRI) shows intraparenchymal perfusion of the kidney, RRI is used to show perfusion in acute and chronic diseases of the renal parenchyma, especially as a result of the widespread use of ultrasonography(USG) in recent times. In addition, Boddi reported that RRI is a strong indicator of mortality and a diagnostic marker, especially in patients with persistent AKI. Many studies have shown that RRI is a promising marker for early detection of renal injury. Patients who develop AKI often require renal replacement therapy (RRT), but there is generally no consensus on the optimal timing of the initiation of RRT. RRT is an invasive procedure. The desired outcome in patients with AKI is normalization of renal function without invasive intervention. However, a more conservative approach to initiating RRT in the course of AKI may expose the patient to adverse outcomes. Therefore, designing a marker that predicts the likelihood of a more severe AKI progression would help us to better make decisions regarding the optimal timing of RRT initiation. In this study, we aimed to evaluate the appropriateness of using the RRI, a noninvasive procedure, to detect progression in AKI stages and the need for RRT in intensive care unit patients.