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  • Acute kidney injury (AKI) is a clinical syndrome generally defined by an abrupt reduction in kidney functions as evidenced by changes in serum creatinine (Scr), blood urea nitrogen (BUN), and urine output.

  • RIFLE (Risk, Injury, Failure, Loss of Kidney Function, and End-Stage Renal Disease), AKIN (Acute Kidney Injury Network), and the Kidney Disease: Improving Global Outcomes (KDIGO) Clinical Practice Guidelines are three criteria-based classification systems developed to define and stage AKI in different patient populations (Table 73–1).

  • All three staging systems have been validated across different patient populations and their staging correlates closely with hospital mortality, cost, and length of stay.

  • Scr and urine output are the main diagnostic criteria for each staging system.

TABLE 73–1abcRIFLE, AKIN, and KDIGO Classification Schemes for Acute Kidney Injurya

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