El-sadek AE, , et al. - Experts sought to correlate the ability of plasma cystatin C and the renal resistive index (RRI) to predict acute kidney injury (AKI) early in critically ill neonates. In neonatal intensive care units, they assigned a sum of 60 critically ill neonates to three groups: group 1 (cases) of thirty participants fulfilling the AKI diagnostic criteria of neonatal Kidney Disease Improving Global Outcome, group 2 of thirty participants not fulfilling the criteria, as well as the 3rd group of thirty age- and gender-matching healthy participants. In comparison with the other two groups, Group 1 showed a significantly high mean cystatin C level during the 1st day of incubation. In all groups, serum creatinine and RRI were insignificantly different. The outcomes showed that the level of plasma cystatin C improved 48 h before both RRI and serum creatinine did in critically ill neonates who developed AKI, so in comparison with serum creatinine and RRI it is more reliable in predicting AKI in critically ill neonates.