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Review
. 2011 Apr;7(4):209-17.
doi: 10.1038/nrneph.2011.13. Epub 2011 Feb 22.

Acute kidney injury: what's the prognosis?

Raghavan Murugan  1 , John A Kellum
Affiliations
Review

Acute kidney injury: what's the prognosis?

Raghavan Murugan et al. Nat Rev Nephrol. 2011 Apr.

Abstract

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.

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Conflict of interest statement

Competing interests

R. Murugan and J. A. Kellum declare an association with the following company: Baxter. J. A. Kellum declares associations with the following companies: Alere, Abbott Laboratories, Astute Medical, Gambro. See the article online for full details of the relationships.

Figures

Figure 1
Figure 1
Conceptual model of AKI. The new conceptual model of AKI incorporates changes in renal function and structure. It also illustrates the potential inverse relationship that may exist between changes in renal function as well as renal structure as captured by injury biomarkers. *Risk incorporates both patient susceptibilities (for example, advanced age) as well as exposures (for example, sepsis). When susceptibilities are great, exposure may be limited but still result in AKI. Abbreviations: AKI, acute kidney injury; GFR, glomerular filtration rate.
Figure 2
Figure 2
RIFLE criteria for diagnosing AKI. The classification system includes separate criteria for creatinine and urine output. A patient can fulfill the criteria through changes in serum creatinine levels or changes in urine output, or both. The criteria that lead to the most severe stage should be used. Note that the F stage of RIFLE is present even if the increase in serum creatinine concentration is under threefold as long as the new serum creatinine level is >350 μmol/l in the setting of an acute increase of at least 44 μmol/l. The shape of the figure denotes the fact that more patients (high sensitivity) will be included in the mild category, including some without actually having kidney damage (less specificity). By contrast, at the bottom of the figure the criteria are strict and therefore specific, but some patients will be missed. Abbreviations: AKI, acute kidney injury; ESRD, end-stage renal disease; RIFLE, Risk, Injury, Failure, Loss, and End-stage renal disease. Permission obtained from BioMed Central © Bellomo, R. et al. Crit. Care 8, R204–R212 (2004).
Figure 3
Figure 3
Incidence of various organ failure among critically ill patients. Rates of organ dysfunction in 3,417 adults with or without sepsis treated in 198 intensive care units in 24 European countries. Figure constructed from data reported in Vincent, J.L. et al. Abbreviation: CNS, central nervous system.
Figure 4
Figure 4
Risk of AKI varies by definition used and timing of assessment. The relationship between application of RIFLE criteria and the apparent incidence of AKI varies according to the definition used and the time at which it is applied, which can lead to underestimations in the incidence of AKI. Abbreviations: AKI, acute kidney injury; RIFLE, Risk, Injury, Failure, Loss, and End-stage renal disease.
Figure 5
Figure 5
Theoretical next generation in AKI diagnosis and classification. This future classification system would likely have two domains, one for measures of function and one for measures of damage. The functional domain, unlike the existing RIFLE criteria, might also require persistent change over a longer duration (for example, 48–72 h) to acknowledge that very transient functional impairment is unlikely to be as important as persistent changes. The damage domain would likely include biomarkers (listed as A–C) from different cell types (for example, tubular epithelial cells, mesangial cells, and vascular endothelium). Classification of ‘risk’ might only require small changes in one marker while ‘failure’ might require more than one changes in several markers or possibly large changes in a single marker. Importantly, analytical cutoffs for injury markers can be set to the corresponding functional impairment level so as to give improved construct validity to the system. Abbreviations: AKI, acute kidney injury; ESRD, end-stage renal disease; RIFLE, Risk, Injury, Failure, Loss, and End-stage renal disease.
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References

    1. Uchino S, et al. Acute renal failure in critically ill patients: a multinational, multicenter study. JAMA. 2005;294:813–818. - PubMed
    1. Hoste EA, et al. RIFLE criteria for acute kidney injury are associated with hospital mortality in critically ill patients: a cohort analysis. Crit Care. 2006;10:R73. - PMC - PubMed
    1. Ali T, et al. Incidence and outcomes in acute kidney injury: a comprehensive population-based study. J Am Soc Nephrol. 2007;18:1292–1298. - PubMed
    1. Alejandro V, et al. Mechanisms of filtration failure during postischemic injury of the human kidney. A study of the reperfused renal allograft. J Clin Invest. 1995;95:820–831. - PMC - PubMed
    1. Myers BD, et al. Nature of the renal injury following total renal ischemia in man. J Clin Invest. 1984;73:329–341. - PMC - PubMed

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