The normal aging process induces structural and functional changes in the kidney characterized by progressive development of glomerulosclerosis and interstitial fibrosis. The timing of these changes is highly variable and is not necessarily inevitable, and appears to hinge on associated comorbid factors. Nearly one-third of the elderly population will not demonstrate a decrement in glomerular filtration rate (GFR) with aging. Nevertheless, the average individual can expect to lose 0.8 mL/min/1.73 m2/year. Because the decline in GFR in individuals with aging is masked by a proportional decline in muscle mass, the serum creatinine generally remains constant. Failure to understand this fact can result in inappropriate dosing of medications with their associated morbidity. It can also result in underrecognition of renal pathology, for even subtle increases in serum creatinine in the elderly can represent a significant loss of renal function. This chapter reviews aspects of renal disease that are prevalent in the geriatric population.
There has been an increase in the prevalence of renal disease with increasing age as a consequence of improved patient survival with comorbid conditions that result in renal dysfunction, such as congestive heart failure, hypertension, diabetes, and atherosclerotic vascular disease. Currently, more than 20% of individuals older than age 65 years who are living in the United States have some degree of renal impairment, and 60% of the patients with end-stage renal disease (ESRD) who are on chronic dialysis are older than age 65 years. Men and women are affected equally. This is surprising given the higher incidence of renal disease in young men; however, these statistics may reflect the higher survival rate for women in general.
The true incidence of acute renal failure (ARF) in the elderly population is unknown. Multicenter studies from Europe report a threefold increase in the prevalence of ARF in older people. In a recent prospective multicenter European study of ARF involving hospitalized patients, more than 60% were older than age 60 years, with about one-third being older than age 70 years. The most frequent causes of ARF were acute tubular necrosis (ATN) (45%), prerenal azotemia (21%), acute on chronic renal failure (CRF) (13%), and obstructive uropathy (10%). Nearly half of the patients who later developed ARF had normal renal function on presentation to the hospital, and the mortality rate was 45%. The incidence of prerenal azotemia in the elderly population is probably much higher; data from a series of elderly patients in the United Kingdom and Spain show that of 571 patients with azotemia, approximately 40% had evidence of prerenal ARF.
The true incidence of glomerular disease cannot be determined in elderly patients because there are no population-based studies. Until recently, glomerulonephritis in geriatric patients received little attention because of fear of an increased risk of morbidity and mortality associated with renal biopsy, and to the more difficult interpretation of histopathological findings. The increased proportion of elderly people entering renal replacement therapy programs has prompted nephrologists to reconsider ...