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As the elderly population continues to grow, the diagnosis and treatment of renal diseases become challenges for the everyday nephrology practice. Although elderly patients are prone to the same diseases of the kidney as younger patients, the diagnostic criteria are not so clearly defined. Anatomic and functional age-induced changes often overlap pathologic processes. The resulting reduced renal function decreases the individual's capacity to respond to a variety of stresses and has important clinical implications for diagnosis and treatment. Comorbid conditions, the absence of classic symptoms, “symptomless” conditions in those with impaired consciousness, and the poor correlation between clinical presentation and the etiology of disease make the diagnosis of renal diseases in the elderly even more difficult. Finally, several pathologic conditions of the kidneys might occur simultaneously in the elderly.
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General Considerations
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Acute renal failure (ARF) is more frequent in elderly patients than in younger patients and it is often due to multiple causes. Predisposing factors are age-related changes in renal structure and function. The incidence of ARF is estimated to involve 6–10% of all admissions of the elderly to an acute medical service.
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The most frequent causes of ARF are nephrotoxic drugs, sepsis, and hypoperfusion. Radiocontrast-induced ARF and postoperative ARF are still very frequent (occurring in about 17% and 25% of cases, respectively).
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About 50% of the patients with ARF have a prerenal etiology and the majority of them have only mild renal impairment. Oliguria is not a prominent finding in ARF in the elderly and cases of nonoliguric ARF may go unrecognized. This may result in overdosing patients with renally excreted medications (digitalis, gentamicin). Hypophosphatemia and hypokalemia, when present, most probably reflect the severity of the underlying disease or malnutrition.
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The treatment of patients with ARF requires careful monitoring of fluid and electrolyte balance. It is very important to prevent malnutrition since hypercatabolism is a frequent finding in elderly patients with ARF; nutritional support should be implemented during the early phase since such patients may lose about 0.5 kg of body mass per day. On the other hand, fluid restriction will delay recovery from ARF and lead to a deterioration in central nervous system function. In patients with advanced renal failure standard dialytic techniques including slow continuous methods should be applied.
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The prognosis differs depending on the underlying disease since age itself does not have a significant impact on the prognosis of patients with ARF. The aged kidney retains the capacity to recover from acute ischemic or toxic injury over several weeks. However, care should be taken to avoid nephrotoxins, radiocontrast agents, and volume depletion. The overall mortality rates correlate with the severity of clinical disease ranging between 40% and 60%. Aortic aneurysm repair had very high mortality (as high as 100% in some series) but ...