Screening for and Staging Chronic Kidney Disease
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Chronic kidney disease (CKD) is increasingly common among older adults. In the older individual, the presence of CKD is predictive of cardiovascular death, increased all- cause mortality, and progression to end-stage renal disease and the need for dialysis. Early identification of these high-risk individuals may prevent or delay such adverse outcomes. The Canadian Society of Nephrology (CSN) released a position statement in September 2006 suggesting that screening be limited to those at high risk. We recommend that clinicians follow the CSN algorithm for screening for CKD among older adults.
Key words: chronic kidney disease, estimated glomerular filtration rate, older adults, renal function, screening.
Introduction
Chronic kidney disease (CKD) is increasingly common among older adults.1 In the older individual, the presence of CKD is predictive of cardiovascular death, increased all- cause mortality, and, less so, progression to end-stage renal disease (ESRD) and the need for dialysis.2,3 Early identification of these high-risk individuals may prevent or delay such adverse outcomes. The purpose of this review is threefold--to define and classify CKD, to discuss how best to measure renal function in clinical practice, and to discuss the health impact of CKD on our aging population.
CKD Staging
In 2002, the National Kidney Foundation Kidney Disease Outcomes Quality Initiative (NKF KDOQI) led the way by developing a staging system and classification for CKD.4 This staging system had the advantage of being clearly defined, reminding physicians that, with time, a large proportion of patients progress through the five stages of CKD and become at risk of requiring dialysis or kidney transplantation; it replaced loosely used terms such as chronic renal failure, kidney failure, end-stage renal disease, and renal insufficiency. Stages are based largely upon either the measured glomerular filtration rate (GFR)(Animation 1) or estimated GFR (eGFR) and are divided into five levels, with each stage suggesting a higher degree of irreversibility and scarring (Table 1, Figure 2). Often forgotten are those at risk of renal disease (stage 0) for whom screening is essential, such as individuals with a >5-year history of diabetes or those with a family history of hereditary renal disease. Staging has been adopted widely throughout the nephrology community and is often used to develop specialized clinics that provide the necessary multidisciplinary team care.
Animation 1
Screening for CKD
The Canadian Society of Nephrology (CSN) released a position statement in September 2006 (www.csnscn.ca) that suggested that screening be limited to those at high risk, such as individuals with diabetes or hypertension or those with vascular disease (Figure 1). Furthermore, CSN acknowledged that many patients with CKD stages 1-3 have low risk of progression. Based on the latter observation, CSN currently recommends that patients with CKD stage 3, in whom eGFR has remained stable over 6-12 months, be managed without immediate nephrology referral unless there are additional symptoms or signs of concern. These individuals require serial measurements at regular intervals (3-6 monthly would be most appropriate for most cases).
The definition of “normal” renal function in the