This work has been fulfilled to reveal the prevalence of acute kidney injury (AKI) as a complication among critically ill patients admitted to pediatric intensive care unit, and the role of serum neutrophil gelatinase associated lipocalin (NGAL) in early prediction of development of such complication, which has been found to be a novel biomarker for that purpose, and also a novel indicator for the prognosis and survival rate among those patients.