Aging is an inevitable biological process that affects many organ systems, of which the kidney is one of the most significantly affected. The process of aging is associated with renal changes, both physiologic and anatomical that differentiates the aged kidney from a younger one. These changes increase suspectibility to kidney injury and may lead to decline in kidney function. Apart from age associated changes in the kidney, older adults are more likely to have associated chronic medical conditions such as hypertension, diabetes mellitus (DM), issues with polypharmacy and exposure to other nephrotoxins. These conditions may further predispose older adults to chronic kidney disease (CKD) and in some cases ultimately lead to end-stage kidney disease (ESKD).
With an aging population that continues to grow, the prevalence of kidney disease tends to be higher in older adults. As a result of this, physicians increasingly have to manage older adults with acute kidney injury (AKI), various stages of CKD, as well as other renal pathologies. It is therefore imperative for clinicians, especially nephrologists, to acquire adequate knowledge about the unique characteristics of an aged kidney and its associated clinical implications in older adults.
In this chapter, we explore the structural and physiological changes that occur in the aging kidney, the common causes and treatment of kidney diseases in older adults, and unique challenges in managing older adults with kidney disease. For the purpose of this review, “older adults” will be used to describe persons age 65 years and older.
ANATOMICAL AND PHYSIOLOGICAL CHANGES IN THE AGING KIDNEY
With normal aging, structural and functional changes occur in the kidneys. These changes are different from those that are disease-mediated. The decline in kidney function noted with normal aging is associated with preserved proximal tubular function and normal serum erythropoietin, hemoglobin levels, serum urea, urinalysis as well as normal metabolic indices such as phosphorus, calcium, parathyroid hormone. This is further supported by the fact that only a small proportion of older adults with decline in kidney function progress to ESKD.
The major histological features of renal aging are arterial intimal fibrosis as well as glomerulosclerosis, tubular atrophy and interstitial fibrosis. Structural and functional changes in normal aging are summarized in Table 55–1. These structural changes in older adult kidneys result in decrease in the total kidney volume with aging especially after age 50 years. In addition, there are several radiological changes that are more evident in the aging kidney such as kidney cysts, focal scars, increased cortical surface roughness and medullary volume, and decreased parenchymal thickness.
Table 55–1.Changes in kidney with normal aging. |Favorite Table|Download (.pdf) Table 55–1. Changes in kidney with normal aging.
|Affected Parts of Kidney ||Structural Changes ||Functional Changes |
- Globally sclerosed glomeruli
- Glomerular ischemia
- Decrease number of functional glomeruli
- Compensatory hypertrophy ...