The development of effective therapies for acute kidney injury (AKI) has been hindered by delayed diagnosis in the clinical setting, varying definitions of AKI, and limited prognostic information. In a study by Portilla et al., elevations in liver fatty acid-binding protein (L-FABP) were found to predict AKI in children undergoing cardiac surgery. New biomarkers offer the promise of earlier and more accurate diagnosis of AKI. Before they can be deemed clinically useful, however, they must undergo rigorous validation in multiple cohorts.