Epidemiology of cardiac surgery-associated acute kidney injury.

Acute kidney injury (AKI) is defined by the KDIGO definition into 3 stages on basis of an increase in serum creatinine or a period of oliguria. AKI is defined as rapid reversal when the episode is 48 h or less. When AKI persists for 7 days or longer, the term acute kidney disease is used. Subclinical AKI is defined by increased concentration of an AKI biomarker, without meeting the KDIGO definition for AKI. In contrast to this, functional AKI is defined by the KDIGO definition, wherein the AKI biomarker concentration is not increased. AKI is multifactorial and heterogeneous and occurs in half of ICU patients as defined by the current KDIGO definition for AKI. In this review, we specifically describe the epidemiology of cardiac surgery-associated AKI and describe the role of scoring systems and specific AKI biomarkers.