Chronic kidney disease (CKD) has multiple causes, all characterized by progressive loss of nephrons and kidney function, and frequently leading to end-stage renal disease (ESRD). The prevalence of CKD is 32.6% in people over age 60 compared with 14.8% in the overall US population. It is important not to confuse normal age-related reduction in kidney function with CKD. But, early recognition/ treatment of CKD can slow loss of renal function, reduce the risk of ESRD, and improve quality of life.

Estimating Kidney Function

Kidney function is measured in terms of blood filtration through the renal filtering system and is called “estimated glomerular filtration rate” or eGFR. The higher the eGFR, the better the kidneys are functioning. There are a number of eGFR calculators available, but it is unclear which are most accurate in older adults.

Classically, eGFR calculators relied on serum creatinine levels, but creatinine levels can be affected by the loss of muscle mass that often accompanies aging. More recently, blood cystatin C levels have been used to estimate eGFR and are more accurate as cystatin C is less affected by loss of muscle mass. If cystatin C is not available, current recommendations are to use the MDRD, CKD-EPI, or BIS equations (Table 1). However, renal dosing for many drugs, especially older ones, is based on the older Cockroft Gault equation. When prescribing for patients with CKD, check the drug manufacturer’s prescribing information about which approach was used to determine renal dosing.

Finally, note that renal function cannot be reliably assessed with creatinine levels alone. Age, sex, and race are also important and are considered in the various equations.

The Aging Kidney

There is a natural decline in renal function (and measured eGFR) with age due to loss of renal mass and damaged kidney filtering mechanisms. Renal function steadily declines starting at about age 30, with the steepest decline occurring after age 75. Generally, however, reductions in renal function do not progress to the point of ESRD. The natural age-related decline in renal function can often be differentiated from Chronic Kidney Disease by the lack of proteinuria, lack of biochemical abnormalities, and lack of concomitant chronic illnesses associated with impaired renal function.

Causes of Chronic Kidney Disease

Major causes of CKD in older adults include hypertension, diabetes mellitus, ischemic nephropathy, and urinary tract obstruction. In addition, long-term use of proton-pump inhibitors has recently been linked to Chronic Kidney Disease.

Type-2 diabetes and systolic hypertension have the largest effect on progression of Chronic Kidney Disease in older adults. Fortunately, disease progression can be slowed by appropriately treating these conditions. Older adults with CKD are more susceptible to acute kidney injury (AKI) events, which in turn, may contribute to further progression of Chronic Kidney Disease.

Screening for Chronic Kidney Disease

The US Preventive Services Task Force states that there is insufficient evidence to assess the benefits and harms of screening for Chronic Kidney Disease in asymptomatic adults. However, it is common in practice for older adults to have an assessment of renal function as part of their annual medical evaluation.

Guidelines suggest diagnosing CKD and initiating further evaluation in any patient with an eGFR of <60ml/min/1.73m² or other markers of kidney damage (e.g., proteinuria, elevated creatinine level) for more than 3 months. Recently, however, there have been proposals that a diagnosis of Chronic Kidney Disease in older adults should not be made in the absence of other indicators of CKD unless the eGFR is below 45ml/min/1.73m² (see Glassock article on references and resource list).

Management of CKD

Management relies on modifying risk factors to slow the progression of CKD. Agents such as angiotensin-converting enzyme inhibitors (ACEIs) or angiotens in receptor blockers (ARBs) may be used when patients have proteinuria to improve glomerular filtration. These drugs, however, may also predispose older patients to acute kidney injury by decreasing overall vascular perfusion of the kidneys; they can also cause hyperkalemia. Renal function and potassium levels should be checked one to two weeks after starting or increasing the dose of ACEIs or ARBs.

Treatment also involves addressing known underlying risk factors, such as blood pressure and glycemic control. In addition, case should be taken to dose a patient’s medications based on GFR (Table 2), and medications known to damage kidneys should be avoided. Major culprits include non-steroidal anti-inflammatory drugs, radio contrast agents, aminoglycosides, amphotericin B, calcineurin inhibitors, and others. Efforts to reduce the number and severity of acute kidney injury episodes is another important component of CKD management.

When is Specialty Care Needed?

Referral to a nephrologist should be considered when the eGFR is <45 ml/min/1.73m², when renal function is trending downward, when proteinuria is present, or when a medical condition is thought to be contributing to reduced eGFR.

Associated Disease Concerns

Older adults with Chronic Kidney Disease are at higher risk of developing cardiovascular disease, malnutrition, physical disability, frailty, and cognitive decline. A multidisciplinary care approach focusing on cardiovascular risk factor modification should be included in the goals of treatment for these patients. Clinicians caring for older adults with CKD should also incorporate preservation of functional status as a component of routine care.

It is important to identify Chronic Kidney Disease in older adults in its early stages so that necessary resources can be organized to provide appropriate care. Simplification of medication regimens, support from ancillary health care workers, emphasis on maintaining physical activity, and other principles of geriatric care are particularly applicable to older adults with Chronic Kidney Disease.

References and Resources

• Fung E, Kurella Tamura M. Epidemiology and public health concerns of CKD in older adults. Adv Chronic Kidney  Dis. 2016;23(1):8-11.
• Glassock R, Delanaye P, El Nahas M. An age-calibrated classification of chronic kidney disease. JAMA. 2015;314(6):559-560.
• National Institute of Diabetes and Digestive and Kidney Diseases
• National Kidney Foundation
• United States Renal Data System. 2016 USRDS annual data report: Epidemiology of kidney disease in the United States
• National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases,  Bethesda, MD, 2016

Interprofessional care improves the outcomes of older adults with complex health problems

Elder Care Editors: Editor-in-Chief: Barry D Weiss, MD;  Deputy Editor: Mindy Fain, MD

 National Editorial Board:  Theodore M Johnson II, MD, MPH, Emory University; Jenny Jordan, PT, DPT, Sacred Heart Hospital, Spokane, WA;  Jane Marks, RN, MS, FNGNA, Johns Hopkins University; Josette Rivera, MD, University of California San Francisco; Jean Yudin, CRNP, University of Pennsylvania

Interprofessional Associate Editors: Carleigh High, PT, DPT; David Coon, PhD; Marilyn Gilbert, MS, CHES; Jeannie Lee, PharmD, BCPS; Marisa Menchola, PhD;  Francisco Moreno, MD; Linnea Nagel, PA-C, MPAS; Lisa O’Neill, DBH, MPH; Floribella Redondo; Laura Vitkus, MPH, CHES

Published by: The University of Arizona, PO Box 245027, Tucson, AZ 85724-5027  |  (520) 626-5800  | https://uofazcenteronaging.co

 This project was supported by the Health Resources and Services Administration (HRSA) of the U.S. Department of Health and Human Services (HHS) under grant number U1QHP28721, Arizona Geriatrics Workforce Enhancement Program. This information or content and conclusions are those of the author and should not be construed as the official position or policy of, nor should any endorsements be inferred by HRSA, HHS or the U.S. Government.