Comparison of different definitions of acute kidney injury in extremely low birth weight infants

The definition of acute kidney injury (AKI) has evolved over the years, and three definitions have been adapted including pediatric risk injury failure, loss of kidney function (pRIFLE), Acute Kidney Injury Network (AKIN), and Neonatal Modified Kidney Disease Improving Global Outcomes (KDIGO). We sought to report the prevalence and outcome of (AKI) according to the three existing definitions in extremely low birth weight (ELBW) infants.

In a retrospective cohort study, medical records of all ELBW infants (<1000 g) admitted to our neonatal intensive care unit (NICU) between Jan 2002 and Dec 2011 were reviewed. Infants' demographics, anthropometric measurements, and clinical characteristics were collected at the time of birth and at discharge from the NICU. Infants were staged according to the three different definitions.

During the study period, 483 ELBW infants met our inclusion criteria. The incidence of AKI was 56, 59, and 60% according to pRIFLE, AKIN, and KDIGO, respectively. Mortality, NICU length of stay, and serum creatinine (SCr) at NICU discharge were higher in infants with advanced AKI stages regardless of the definition. In addition, discharge NICU weight and length z scores were lower in infants with advanced AKI stages. SCr at 72 h of life and SCr peak were predictable of NICU mortality [AUC 0.667 (95% CI 0.604-0.731), p < 0.001 and AUC 0.747 (95% CI 0.693-0.801), p < 0.001, respectively].

Regardless of the definition, advanced AKI is associated with increased mortality, prolonged NICU length of stay, and poor growth in ELBW infants. SCr at 72 h of life and SCr peak may be predictable of NICU mortality.