Acute Kidney Injury and Early Diagnostic Biomarkers: A Narrative Literature Review

Introduction. Acute kidney injury (AKI) is a serious entity characterized by sudden impairment of renal function in hospitalized patients, particularly in the intensive care unit, resulting in high morbidity and mortality. Current diagnostic methods based on changes in serum creatinine (sCr) and urine output are prone to many confounding variables. The aim of this study is to investigate the role of specific biomarkers, namely NGAL, Cystatin C, IL-18, and KIM-1, in the diagnosis of AKI. Materials and methods. In this literature review, a thorough search of the PubMed, Scopus and Google Scholar databases was conducted to investigate the early diagnostic potential of NGAL, Cystatin C, IL-18, and KIM-1 in AKI patients. Biomarkers. Neutrophil Gelatinase-Associated Lipocalin (NGAL), both serum and urinary, was discovered to rise shortly after AKI onset, several hours before sCr elevation, differentiating AKI from chronic kidney disease and prerenal azotemia. Cystatin C (CysC), a protein constantly produced and filtered, was identified as a reliable marker for AKI, although its high cost prohibits its use. Interleukin-18 (IL-18), a pro-inflammatory cytokine, demonstrated potential, particularly in critically ill and post-cardiovascular surgery patients, although results on its predictive ability were inconsistent. Kidney Injury Molecule-1 (KIM-1), a protein released into urine after proximal tubular injury, demonstrated high sensitivity and specificity shortly after AKI onset, while it has been associated with a number of kidney diseases. Conclusions. Novel biomarkers (NGAL, CysC, IL-18, and KIM-1) provide a faster and more accurate diagnosis of AKI than traditional methods in various clinical settings. Additional research is required to fully incorporate these promising molecules into everyday clinical practice.