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Chronic kidney disease (CKD) is an emerging public health problem in Canada and throughout the world.
Defined as either kidney damage or a glomerular filtration rate (GFR) less than 60 ml/min/1.73 m2 ,
CKD can be classified into 5 stages according to the K/DOQI CKD classification scheme
Classification of Chronic Kidney Disease by Pathology, Etiology and Prevalence in Patients With End-Stage Renal Disease
Kidney failure requiring dialysis or transplantation (Stage 5 CKD) is the most visible outcome of CKD.
The prevalence of Stage 5 CKD varies considerably in the developed world:
- United States - 1400 patients per million population (2003 USRDS Annual Report)
- Canada - 774 patients per million population (2001 CORR Report)
- Germany - 693 patients per million population (1998)
- Australia - 580 patients per million population (1998)
- Japan - 1557 patients per million population (1998)
Even in Canada, the prevalence ranges from 680 patients per million population in Saskatchewan to 1006 patients per million population in Manitoba. The variability in prevalence is multifactorial. In addition to population differences in risk factors for CKD (such as diabetes, age, race, and hypertension), under-recognition and under-treatment of CKD may account for some the variability across Provinces and Countries.
The prognosis of patients with Stage 5 CKD is bleak. In Canada the median 5-year survival for these patients is 34% for diabetics and 53% for non-diabetics. Most patients cannot maintain full-time employment. Health care costs are also excessive with ~ 2% of the Canadian health care budget being spent on this small (0.1%) segment of the population.
Underlying this relatively small number of individuals with Stage 5 CKD is a very large group of individuals with less severe degrees of kidney dysfunction. In the United States it is estimated that one in nine adults have some form of CKD. This CKD may be a reduction in GFR, excessive urine protein loss, or some other form of kidney damage. In Australia, ~ 16% of all adults have CKD. Canadian estimates are lacking across the full adult age spectrum. In Southern Alberta, we have previously shown the ~ one in five adults aged greater than 65 years have CKD as manifest by a GFR less than 60 ml/min/1.73 m2.
Given the varied prevalence of CKD across the stages of CKD, it appears intuitive that most patients with CKD will die before the need for dialysis or kidney transplantation. Recently, using data collected from a managed care group in the United States, researchers at Oregon Health and Science University demonstrated that in patients with Stage 4 CKD, the risk for death over 5 years was 9.1% per year, 2 times greater than the risk for needing dialysis. For patients with Stage 3 CKD, the risk for death was 4.9% per year, 20-fold greater than the risk for dialysis. According to an analysis from the United Kingdom Prospective Diabetes Study, the 10-year risk for death is 10 times greater than the risk for needing dialysis in patients with baseline diabetes and Stage 1 or 2 CKD. The most common cause of death in these patients with CKD is related to cardiovascular disease.
Historically, the evaluation and management of CKD has focused on the diagnosis and treatment of specific kidney diseases, and dialysis or transplantation for kidney failure. Evidence accrued over the last ten years indicates that many of the adverse outcomes associated with CKD, including progression of CKD and cardiovascular disease, can be prevented or delayed through early intervention. Unfortunately, the under-diagnosis of CKD leads to missed opportunities to prevent complications and adverse outcomes associated with CKD.
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