Does the High Renal Resistive Index Reveal an Increased Risk of Acute Kidney Injury? A Protocol for Systematic Review.

<b>Introduction.</b> Acute Kidney Injury (AKI) is a serious complication in critically ill patients associated with significant morbidity and mortality. Early detection and risk stratification remain challenging, particularly in complex conditions such as septic shock where hemodynamic alterations complicate the clinical picture. Renal Resistive Index (RRI), measured through Doppler ultrasonography, has emerged as a promising non-invasive tool for assessing renal hemodynamics and microcirculatory changes. While various studies have investigated the relationship between RRI and AKI, there has not been a comprehensive systematic evaluation of RRI's utility in predicting and assessing AKI in critical care settings. <b>Objective.</b> The main aim is to evaluate the difference in RRI between patients who manifested AKI and patients who did not manifest AKI. Furthermore, the risk of AKI occurrence related to RRI will be computed. <b>Methods.</b> We will perform systematic research in PubMed and Scopus according to the PRISMA Guidelines. We will screen observational studies, with both retrospective and prospective designs on critically ill patients, without sex or age restriction. <b>Expected results.</b> This systematic review is expected to provide a comprehensive and extensive evaluation of the relationship between RRI and AKI. It will be based on observational studies, as RRI is a risk factor not subject to control by the investigator. In addition to assessing the association between RRI and AKI, the study also aims to highlight potential gaps in current knowledge and suggest directions for future research. <b>Conclusions.</b> The present systematic review protocol will include all existing evidence from published articles evaluating the RRI values in patients manifesting or not AKI.