“…Preliminary findings have shown that the etiology and prevalence of AKI vary, mainly due to different aspects of the sample evaluated (i.e., animal species, sex, age, and comorbidity), differences in the income levels of countries (with low-to-middle income countries showing more severity and a higher incidence of AKI than high-income countries), and differences in AKI classification criteria [32,38,43,44]. Throughout the last two decades, the AKI definition has been mainly based on the RIFLE (Risk, Injury, Failure, Loss, End-Stage Kidney Disease), Acute Kidney Injury Network (AKIN), and Kidney Disease: Improving Global Outcomes (KDIGO) criteria and stages [43,44]. Until 2004, the diagnosis of AKI was based on urine output as well as blood urea nitrogen (BUN) and serum creatinine (SCr) levels.…”