Urinary biomarkers in acute kidney injury

Acute kidney injury (AKI) is common in critically ill patients and is associated with high mortality and cost of hospitalization. The standard clinical diagnosis of AKI is based on the estimation of serum creatinine, which is a late and unsatisfactory marker of AKI. An intense search for an early biomarker has yielded considerable success in recent years and several urinary biomarkers to predict AKI early and reliably have been identified. Among these, urinary concentration of neutrophil gelatinase-associated lipocalin (NGAL) holds much promise and has been validated in several population of AKI in intensive care unit (ICU). Concentrations of other urinary biomarkers such as kidney injury molecute-1 (KIM-1), interleukin-18 (IL-18) and Liver fatty acid binding protein (L-FABP) are promising, but await validation. Sensitivity and specificity of urine NGAL (uNGAL) to predict AKI is best in homogeneous population and pediatric patients, but somewhat less in heterogeneous adult population in ICU. In addition, uNGAL predicts severe AKI, renal replacement therapy initiation and mortality in ICU. In future, further studies are likely to clarify and broaden the application of urine biomarkers in research and clinical practice in AKI. Future holds much promise in terms of therapeutic interventions based on biomarkers for primary and secondary prevention in AKI.