Acute kidney injury: what's the prognosis?


Acute kidney injury (AKI) is common (especially during critical illness), increasing in incidence, and is associated with considerable morbidity and mortality. The Risk, Injury, Failure, Loss, and End-stage renal disease (RIFLE) classification currently provides a standardized estimate of incidence and outcomes from AKI. Despite advances in the understanding of the pathogenesis of human AKI, our ability to assess kidney function is limited and functional impairment poorly correlates with structural injury to the kidneys. Emerging novel biomarkers are, however, likely to further enhance risk stratification, facilitate early diagnosis, enable early enrollment in therapeutic trials, and assess prognosis. Sepsis remains the leading cause of AKI among the critically ill and over the past few years insights into the pathogenesis of AKI in sepsis are beginning to shift attention from renal blood flow to inflammation-mediated organ injury. Emerging evidence suggests that survivors of AKI incur long-term risks for developing chronic kidney disease and end-stage renal disease compared with those without AKI. Despite decades of research, no specific therapy for AKI other than supportive care currently exists and further work is required to better understand the pathogenesis of AKI during critical illness and to develop novel treatments.

Key Points

  • Acute kidney injury (AKI) is common and is associated with higher resource utilization and mortality than that of other critical care syndromes

  • Risk, Injury, Failure, Loss, and End-stage renal disease classification is a validated definition of AKI and together with the AKI Network modification is widely accepted

  • Emerging biomarkers may further aid early diagnosis and risk stratification of AKI

  • Current understanding of the pathogenesis and pathophysiology of AKI is poor and treatment is largely supportive

  • AKI increases susceptibility to chronic kidney disease and end-stage renal disease

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Figure 1: Conceptual model of AKI.
Figure 2: RIFLE criteria for diagnosing AKI.
Figure 3: Incidence of various organ failure among critically ill patients.
Figure 4: Risk of AKI varies by definition used and timing of assessment.
Figure 5: Theoretical next generation in AKI diagnosis and classification.


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This publication was made possible in part by funding from grants R01DK070910 and R01DK083961 from the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), the grant KL2RR024154 from the National Center for Research Resources (NCRR), and components of the National Institutes of Health (NIH), and NIH Roadmap for Medical Research. The contents of this Review are solely the responsibility of the authors and do not necessarily represent the official view of NIDDK, NCRR or NIH.

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R. Murugan and J. A. Kellum contributed equally to the discussions, research, writing, editing, and reviewing of this manuscript.

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Correspondence to John A. Kellum.

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R. Murugan and J. A. Kellum declare an association with the following company: Baxter (consultant and grant/research support). J. A. Kellum declares associations with the following companies: Alere (consultant), Abbott Laboratories (consultant), Astute Medical (consultant, grant/research support, patent holder/applicant), Gambro (consultant and grant/research support).

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Murugan, R., Kellum, J. Acute kidney injury: what's the prognosis?. Nat Rev Nephrol 7, 209–217 (2011).

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