Acute kidney injury in the elderly: problems and prospects.

Acute kidney injury (AKI) usually is defined as a decline in glomerular filtration rate over hours to days that can occur either in a person with previously normal kidney function, or in the setting of pre-existing chronic kidney disease. The incidence of AKI has increased steadily in recent years, and this increase is associated strongly with advancing age in the population because epidemiologic data indicate that AKI is much more common in the elderly. In the aging population there is heightened susceptibility to drug toxicity, partially owing to altered drug pharmacokinetics and pharmacodynamics. Furthermore, the elderly consume twice as many medications overall, including nephrotoxic agents, compared with younger patients. The vasodilatory increase in the renal plasma flow and glomerular filtration rate that constitutes renal functional reserve is reduced markedly in healthy elderly individuals, compromising renal adaptation after acute ischemia, and heightening susceptibility to AKI. Age-related alterations in renal tubular function also may heighten susceptibility to AKI because renal sodium conservation in response to dietary sodium restriction is attenuated in the elderly. A recently published study showed that elderly subjects with AKI, particularly those with chronic kidney disease, are more likely to develop end-stage renal disease. The increasing prevalence and extended clinical consequences of AKI in the elderly are of great concern from a clinical and public health perspective.