Biomarkers of early kidney injury in urological patients: From detection to clinical application

This review aims to provide a comprehensive overview of the pathophysiological processes involved in early kidney injury and to evaluate the role of established and emerging biomarkers in facilitating earlier diagnosis, risk stratification, and clinical decision-making, particularly within urological practice. Specifically, the review: (i) outlines the key mechanisms underlying the development of early kidney injury; (ii) examines the current evidence supporting established and novel biomarkers of kidney injury and renal dysfunction; (iii) evaluates their diagnostic, prognostic, and clinical relevance in urology; and (iv) explores existing challenges, future directions, and the potential incorporation of biomarker-guided approaches into precision medicine strategies for kidney injury management. This review examines the underlying mechanisms of early kidney injury, including ischemia, hypoxia, oxidative stress, and the differential contributions of tubular and glomerular damage. Particular attention is given to clinical contexts relevant to urology, such as surgical interventions and obstructive uropathy, where timely detection is essential for preventing irreversible damage. Current and emerging biomarkers are discussed within a pathophysiological framework to provide a more integrated understanding of kidney injury. Tubular injury markers, including neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), and interleukin-18 (IL-18), are highlighted for their ability to detect injury at an earlier stage than traditional measures. In addition, cell cycle arrest biomarkers such as TIMP-2 and IGFBP7 offer predictive value by identifying patients at risk before significant functional decline occurs. The review further explores novel and experimental approaches, including microRNAs, urinary exosomes, and metabolomics-based markers, which may enhance early diagnosis and support precision medicine strategies. Importantly, the clinical relevance of these biomarkers is examined in specific urological settings, including postoperative AKI, contrast-induced injury, obstructive uropathy, and kidney injury associated with renal cell carcinoma. The novelty of this review lies in its integration of mechanistic insights, biomarker biology, and disease-specific urological applications within a single translational framework. Unlike previous reviews that focus primarily on individual biomarkers or general AKI populations, this work emphasizes the relationship between specific injury pathways and biomarker responses, while highlighting emerging precision medicine approaches and their potential role in urological patient care.