Abstract
Acute kidney injury (AKI) is a common clinical syndrome associated with increased morbidity, mortality, length of hospitalization, and long-term risk of chronic kidney disease. In routine practice, AKI is still diagnosed primarily by changes in serum creatinine concentration and urine output. Although these criteria are standardized and clinically useful, they are imperfect markers of early kidney injury because creatinine rises only after a fall in filtration has occurred and urine output is influenced by hemodynamics, medications, fluid balance, and measurement accuracy. This systematic literature review evaluates the role of emerging biomarkers in the early detection and risk stratification of AKI in adults, with particular emphasis on neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), interleukin-18 (IL-18), liver-type fatty acid-binding protein (L-FABP), cystatin C, and the cell-cycle arrest biomarker combination tissue inhibitor of metalloproteinases-2 and insulin-like growth factor-binding protein 7 ([TIMP-2]*[IGFBP7]). The reviewed literature suggests that biomarkers may identify tubular stress or injury earlier than conventional criteria, support risk stratification in selected high-risk populations, and help distinguish functional decline from structural damage. However, heterogeneity of populations, assay platforms, timing of sampling, thresholds, and reference standards limits routine implementation. Biomarkers are best understood as adjuncts to clinical assessment rather than replacements for standard diagnostic criteria.