Recent advances in acute kidney injury epidemiology

Abstract

Purpose of review: Expanding rates of acute kidney injury (AKI) coupled with increasing awareness of its short-term and long-term sequelae have focused efforts to identify patients at risk for this disease and its complications. This review details the recent attempts to identify novel risk factors for AKI, describes further refinements in the diagnostic and prognostic approach using biological markers of injury, and highlights the features of AKI that independently predict poor long-term outcomes.

Recent findings: The presence of proteinuria predicts the development of AKI independently of estimated glomerular filtration rate. Initial results from a large prospective study of AKI biomarkers in cardiac surgery indicate lower agreement with serum creatinine as an AKI standard than observed in early studies. AKI severity and duration are important predictors of chronic kidney disease and long-term mortality. A minority of patients surviving AKI with decreased kidney function is seen by a nephrologist.

Summary: Although the pathophysiologic link is unclear, proteinuria is an easily measurable risk factor for AKI worth considering before anticipated procedures or medication exposures carrying nephrologic risk. Investigation extending beyond agreement with serum creatinine is needed to fully understand the diagnostic and prognostic value of AKI biomarkers. Severity and duration are components of AKI that can help risk-stratify survivors in need of monitoring or nephrology referral.

Figure 1. Incidence of Renal-related Events Grouped by Biomarker and Creatinine Status

(previously published).[32] Haase, et al. using pooled data from 10 prospective observational studies of AKI, examined how different NGAL and creatinine profiles associated with the risk for in-hospital mortality and the need for renal replacement therapy in 2,322 critically ill patients. A stepwise increase in the risk of subsequent renal replacement therapy was observed -NGAL(−)/sCREA(−): 0.0015% versus NGAL(+)/sCREA(−): 2.5% (odds ratio: 16.4, 95% confidence interval: 3.6 to 76.9, p < 0.001), NGAL(−)/sCREA(+): 7.5%, and NGAL(+)/sCREA(+): 8.0%, respectively. Similar trends were findings were observed with hospital mortality (4.8%, 12.4%, 8.4%, 14.7%, respectively) and their combination (4-group comparisons: all p<0.001).

Figure 2. Longitudinal Mortality Rates by Magnitude and Duration of AKI

(previously published).[51] Coca, et al. examined the relationship between duration and magnitude of AKI in 35,302 diabetic patients following cardiac surgery and long-term survival. No increase in mortality rate was observed with increasing AKI severity of short or medium duration. However, the mortality rate increased by duration of AKI within each AKIN stage. The mortality rate for those with AKIN Stage 1 and long duration of AKI is more than 2-fold higher than for those with AKIN Stage 3 and short duration of AKI.[51]

Figure 3. Cumulative Incidences of Nephrology Referral, Dialysis Initiation, Improvement in Kidney Function, and Death Analyzed as Competing Risks

(previously published).[54] Siew, et al. examined outpatient nephrology referrals among 3929 survivors of AKI whose last eGFR up to 30 days following peak injury was < 60 ml/min/1.73 m² in a multi-center Veterans Affairs Cohort. Cumulative incidences of the prespecified outcomes as competing risks during the 12-month surveillance period (30-395 days following peak injury) are shown. Beginning at 30 days following peak injury, the cumulative incidences of first improving kidney function to an eGFR >60 ml/min/1.73 m², dying, being referred to nephrology or receiving dialysis were 44.0% (95% CI: 42.4-45.5), 11.5% (95% CI: 10.5-12.5), 8.5% (95% CI: 7.6-9.4), and 0.2% (95% CI: 0.1-0.4), respectively.