[Urinary biomarkers: A promising tool for modern nephrology]

To avoid the need for renal biopsy, which remains an invasive procedure, numerous urinary biomarkers have been investigated for the detection, risk stratification, and prediction of disease progression in patients with acute or chronic kidney disease. Often referred to as a form of "liquid biopsy," some of these molecular candidates, particularly proteins and peptides, have shown considerable robustness and clinical potential. This review outlines the concept of a biomarker and the key stages involved in its development, drawing on practical examples such as prognostic signatures for antenatal renal developmental abnormalities and the prediction of acute kidney injury, as well as diagnostic applications in common clinical settings, including glomerular diseases using urinary soluble CD163 and acute interstitial nephritis using CXCL9. Methods used for biomarker measurement are also discussed. Despite encouraging results, even the most advanced biomarkers have struggled to progress beyond external multicenter validation because of methodological challenges related to both the underlying technologies and the heterogeneity of patient cohorts. As of 2026, these biomarkers remain primarily research tools, and a broad consensus on their routine clinical use has yet to emerge.