Neonatal acute kidney injury

Overview & Definition

Picture a 26-week, 750-gram infant on day three of life, on mechanical ventilation for respiratory distress syndrome, now with a serum creatinine that has risen from 0.9 to 1.5 mg/dL and a urine output of 0.5 mL/kg/h. Before you dismiss this as "normal prematurity" or blame the indomethacin for the PDA, hold two ideas separate in your mind: the neonatal kidney is uniquely vulnerable, and a rising creatinine is a signal, not noise. [2]

Neonatal acute kidney injury is defined using the neonatal modified KDIGO (neoKDIGO) criteria, adapted from the 2012 KDIGO framework for the neonatal physiology where creatinine reflects maternal creatinine at birth and declines over the first weeks. [1] AKI is present when there is a serum creatinine rise of 0.3 mg/dL or more, or a rise of 50% or more from the previous lowest value, and/or when the urine output falls below 1 mL/kg/h on postnatal days 2 to 7. These criteria are deliberately structured around creatinine and urine output rather than a single threshold, because the neonatal GFR is low, tubular function is immature, and the baseline creatinine is the mother's, not the infant's. [4]

The reason this definition matters is that neonatal AKI is far more common than historically appreciated. The landmark AWAKEN study — a multicentre, multinational cohort of over 2,000 NICU admissions — found an AKI incidence of nearly 30%, with rates varying dramatically by gestational age: nearly 48% in infants below 29 weeks, 18% in those 29 to 36 weeks, and 37% in term infants. [2] More importantly, AKI was independently associated with increased mortality and longer hospital stay after adjusting for confounders — it is not a marker of illness, it is a driver of death. [2]

So the examiner's first question is always: how do you define and recognise AKI in a neonate, and why does it matter? The answer — neoKDIGO criteria, high incidence, independent mortality association — frames the entire management plan. [6]

References10Show ledgerHide ledger

1. [1]Jetton JG, Guillet R, Askenazi DJ, et al Assessment of Worldwide Acute Kidney Injury Epidemiology in Neonates: design of a retrospective cohort study. Frontiers in Pediatrics, 2016.PMID 27486571
2. [2]Jetton JG, Boohaker LJ, Sethi SK, et al. Incidence and outcomes of neonatal acute kidney injury (AWAKEN): a multicentre, multinational, observational cohort study. Lancet Child and Adolescent Health, 2017.PMID 29732396
3. [3]Charlton JR, Boohaker L, Askenazi D, et al. Late onset neonatal acute kidney injury: results from the AWAKEN Study. Pediatric Research, 2019.PMID 30546043
4. [4]Askenazi D, Abitbol C, Boohaker L, et al. Optimizing the AKI definition during first postnatal week using Assessment of Worldwide Acute Kidney Injury Epidemiology in Neonates (AWAKEN) cohort. Pediatric Research, 2019.PMID 30643188
5. [5]Harer MW, Askenazi DJ, et al Association between early caffeine citrate administration and risk of acute kidney injury in preterm infants. JAMA Pediatrics, 2018.PMID 29610830
6. [6]Starr MC, Charlton JR, Guillet R Advances in neonatal acute kidney injury. Pediatrics, 2021.PMID 34599008
7. [7]Bhatt GC, Gogia P, et al Theophylline and aminophylline for prevention of acute kidney injury in neonates and children: a systematic review. Archives of Disease in Childhood, 2019.PMID 30798259
8. [8]Chock VY, Cho SH, et al Aminophylline for renal protection in neonatal hypoxic-ischemic encephalopathy in the era of therapeutic hypothermia. Pediatric Research, 2021.PMID 32503030
9. [9]Kent AL, Charlton JR, et al Neonatal acute kidney injury: a survey of neonatologists' and nephrologists' perceptions and practice management. American Journal of Perinatology, 2018.PMID 28709164
10. [10]Stoops C, Sims B, et al Neonatal acute kidney injury and the risk of intraventricular hemorrhage in the very low birth weight infant. Neonatology, 2016.PMID 27490643