Acute renal failure in the elderly: epidemiology and clinical features.

Structural and functional alterations affecting the aging kidney predispose to an increased risk of acute renal failure (ARF) in the elderly. This is a common problem becoming more relevant because of an increase in life expectancy. The epidemiology of ARF in the elderly is far from being well assessed, because of the lack of uniform definition criteria, variable etiology, coexistence of several comorbidities, and the various clinical settings and geographic areas where the condition is managed, with a higher incidence in developed regions where elderly patients predominate. In 2004, the Acute Dialysis Quality Initiative group proposed the RIFLE criteria for diagnosis and stratification of ARF. More recently, the Acute Kidney Injury Network proposed several refinements to the RIFLE criteria, and the use of the term acute kidney injury (AKI) has been suggested to mean any abrupt reduction in kidney function, while restricting use of the term ARF to severe dysfunction requiring renal replacement treatment. Although in elderly patients the more frequent forms of AKI are functional or obstructive, parenchymal AKI, such as acute tubular necrosis and contrast-induced nephropathy, still frequently occur. Elderly patients with chronic renal disease (CKD) who develop AKI are at high risk for mortality, and are prone to non-recovery from AKI and progression to more advanced stages of CKD and even to end-stage renal disease. Panels of AKI biomarkers are likely to improve early diagnosis and treatment, thus reducing morbidity and mortality of older patients from this condition in the future.