BACKGROUNDAcute kidney injury (AKI) is common in patients treated with extracorporeal membrane oxygenation (ECMO). The RIFLE criteria demonstrate clinical relevance for diagnosing AKI and classifying its severity.OBJECTIVESTo systematically define the incidence, clinical course and outcome of AKI using the pediatric pRIFLE criteria.DESIGNRetrospective, medical records review.SETTINGSPediatric cardiac surgical intensive care units at a tertiary care hospital in Riyadh.PATIENTS AND METHODSWe reviewed the records of all pediatric patients that underwent cardiac surgery and required ECMO postoperatively between 1 January 2011 and 1 January 2016. AKI was classified according to the pRIFLE criteria 48 hours after ECMO initiation. Demographics and concomitant therapies for all patients were collected.MAIN OUTCOME MEASURE(S)Outcome was assessed by recovery from AKI at time of discharge, ICU stay and mortality.RESULTSFifty-nine patients needed ECMO after cardiac surgery during the study period. Their mean (SD) age and weight was 11.0 (16.5) month and 5.5 (3.6) kg, respectively. All patients had a central venoarterial ECMO inserted. Fifty-three patients (90%) developed AKI after ECMO initiation. The majority of patients (57%) were categorized as pRIFLE-Failure, having a higher mortality rate (28/34 patients, 82%) in comparison to the pRIFLE-Injury and pRIFLE-Risk groups. Twenty-nine patients (49%) required either peritoneal dialysis (PD), or renal replacement therapy (RRT) or both. For AKI vs non-AKI patients, there was a statistically significant difference between mean (SD) ECMO duration (9.0 [8.00] vs 6.0 [2.0] days; P=.02) and ICU stay (37.0 [41.0] vs 21.0 [5.0] days; P=.03), respectively. The overall mortality rate was 58%, with a significant difference (P=.03) between AKI and non-AKI groups. All the patients who survived had normal creatinine clearance at hospital discharge.CONCLUSIONThere is a high incidence of AKI in pediatric patients requiring ECMO after cardiac surgery, and it is associated with higher mortality, increased ECMO duration, and increased ventilator days.LIMITATIONSSingle-center retrospective analysis and the small sample size limited the precision of our estimates in sub-populations.