Diagnostic Criteria for Acute Kidney Injury: Present and Future

Abstract

Acute kidney injury (AKI) is a clinical diagnosis guided by standard criteria based on changes in serum creatinine, urine output, or both. Severity of AKI is determined by the magnitude of increase in serum creatinine or decrease in urine output. Patients manifesting both oliguria and azotemia and those in which these impairments are persistent are more likely to have worse disease and worse outcomes. Short- and long-term outcomes are worse when patients have some stage of AKI by both criteria. New biomarkers for AKI may substantially aid in the risk assessment and evaluation of patients at risk for AKI.

Keywords: Acute kidney injury; Biomarkers; Clinical trials; Dialysis; Mortality; Renal recovery; Renal-replacement therapy.

Figure 1

Sensitivity/specificity tradeoffs for various applications of clinical definitions. For research and quality improvement, fixed thresholds are usually needed, while for clinical application diagnoses can be more flexible depending on the actions they elicit.

Figure 2

Diagnostic certainty. Diagnostic certainty is usually low at the outset of a clinical evaluation but improves with time as more information and diagnostic testing results become available.

Figure 3

Various clinical scenarios of Acute Kidney Injury based in function, damage and stress. The change in kidney function (e.g., glomerular filtration rate) is shown in black while damage is shown in grey. Panel A depicts the “classic” case where damage increases and is followed by a decline in function only after some time (time shown on the x-axis). Panels B and C show alternate scenarios where function may change coincidental to or even before damage. The dashed arc represents renal cell stress.