In this review we summarize the world-wide epidemiology of acute kidney injury (AKI) in children with special emphasis on low-income countries, notably those of the sub-Saharan continent. We discuss definitions and classification systems used in pediatric AKI literature. At present, despite some shortcomings, traditional Pediatric Risk Injury Failure Loss and End Stage Kidney Disease (pRIFLE) and Kidney Disease Improving Global Outcomes (KDIGO) systems are the most clinically useful. Alternative definitions, such as monitoring serum cystatin or novel urinary biomarkers, including cell cycle inhibitors, require more long-term studies in heterogenous pediatric AKI populations before they can be recommended in routine clinical practice. A potentially interesting future application of some novel biomarkers could be incorporation into the "renal angina index", a concept recently introduced in pediatric nephrology. The most reliable epidemiological data on AKI in children come from high-outcome countries and are frequently focused on critically ill pediatric intensive care unit populations. In these patients AKI is often secondary to other systemic illnesses or their treatment. Based on a recent literature search performed within the framework of the "AKI 0by25" project of the International Society of Nephrology, we discuss the scarce and often inaccurate data on AKI epidemiology in low-income countries, notably those on the African continent. The last section reflects on some of the many barriers to improvement of overall health care in low-income populations. Although preventive strategies for AKI in low-income countries should essentially be the same as those in high-income countries, we believe any intervention for earlier detection and better treatment of AKI must address all health determinants, including educational, cultural, socio-economic and environmental factors, specific for these deprived areas.
Keywords: Definitions of AKI; Low income countries; Pediatric AKI; Worldwide epidemiology.