Can J Diabetes 38 (2014) 287–289
Contents lists available at ScienceDirect
Canadian Journal of Diabetes journal homepage: www.canadianjournalofdiabetes.com
Editor’s Note
Diabetes and Chronic Kidney Disease: Concern, Confusion, Clarity?
The increasing prevalence of diabetes has been accompanied by a rise in the prevalence of chronic kidney disease. In part, this may be a result of increased life expectancy and reduced cardiovascular mortality. However, increased demand for renal replacement therapy and the appearance of chronic kidney disease in adolescents with type 2 diabetes is of concern for both healthcare providers and payers. Among healthcare professionals, diabetic kidney disease often seems to be a topic they find both concerning and confusing. The concern seems to reflect widespread recognition that kidney disease is an important and serious complication of diabetes. However, there seems to be significant uncertainty about how the kidney disease should be managed and how it impacts other aspects of diabetes care. Anxiety around the issue of diabetes and kidney disease has the potential to result in clinical inertia, driven by a desire to avoid making mistakes. Optimal care for kidney disease requires a team that is motivated but that is also confident in its understanding of the disease. I hope that this nephropathythemed issue of Canadian Journal of Diabetes will help to add clarity for teams taking care of people with diabetes and kidney disease.
What’s in a Name? Several different names are used when talking about kidney disease, and that contributes to some of our confusion. (Figure 1). Chronic kidney disease (CKD) is a nonspecific term describing a long-term reduction in renal function that may or may not be progressive and that may be the result of several different disease processes. Although diabetes is a leading cause of CKD, the disease affects many people who do not have diabetes. Diabetic nephropathy (DN) is a more specific term describing a clinical syndrome of albuminuria, hypertension and a progressive decline in renal function that has typical appearances on kidney biopsy. DN is more common with poor glycemic control and usually develops after more than 10 years of duration of diabetes. Diabetic kidney disease (DKD) is an intermediate term that captures DN and also CKD in people with diabetes due to other causes, including hypertension and atherosclerosis. In people with longstanding type 1 diabetes and histories of albuminuria, DKD is almost invariably due to “pure” DN. In type 2 diabetes, biopsies suggest that DKD is often due to hypertensive or renovascular disease or a combination of the two plus diabetes.
defined by abnormalities in either of these aspects: reductions in the glomerular filtration rate and/or the presence of albumin in the urine. Classically, DN is defined by the presence of albuminuria followed (sometimes years) later by reduced glomerular filtration rate (GFR). Other kidney diseases, particularly renovascular disease, usually present with reduced GFR but without albuminuria. Thus, CKD can be defined based on either reduced GFR or albuminuria or both. People with CKD are at increased risk for cardiovascular disease and for end stage renal disease (ESRD), but the risks seem to be highest in people with CKD who have low GFR and albuminuria (Figure 2). It is important to remember that although albuminuria and GFR are often described as categoric variables (micro-albuminuria, macroalbuminuria, CKD stages 1 through 5), these risk factors behave as continuous variables (see Dr MacFarlane’s article in this issue). What are the Risks? Widespread reporting of estimated GFR (eGFR) derived from serum creatinine levels by diagnostic labs in Canada and around the world has increased the awareness of and anxiety about kidney function but has not necessarily improved care (1). Blood tests are often ordered during illness, when changes in fluid status and medications can cause acute changes in serum creatinine, which in turn are reflected in changes in eGFR. Our guidelines recommend that eGFR should not be used when kidney function is changing rapidly so as to assess the stage of CKD (2). This might be analogous to the advice one would give to a novice investor when seeing a 1-day drop in the price of a stock. It is important that healthcare professionals pay close attention to trends in renal status. A narrow focus looking at current GFR may lead us to overestimate risk for ESRD in an elderly person in whom the eGFR is low but stable, while underestimating the risk in a young person with dipstick-positive proteinuria and proliferative retinopathy with an eGFR of 90 mL/min but a level that has fallen by 10 mL/min over the past year. The risks for ESRD in subjects with type 1 diabetes and CKD is much higher (approximately 10 times higher) than in subjects with type 2 diabetes. Fortunately, modern therapy has seen a significant decline in the proportion of people with type 1 diabetes progressing to ESRD (to
Contents lists available at ScienceDirect
Canadian Journal of Diabetes journal homepage: www.canadianjournalofdiabetes.com
Editor’s Note
Diabetes and Chronic Kidney Disease: Concern, Confusion, Clarity?
The increasing prevalence of diabetes has been accompanied by a rise in the prevalence of chronic kidney disease. In part, this may be a result of increased life expectancy and reduced cardiovascular mortality. However, increased demand for renal replacement therapy and the appearance of chronic kidney disease in adolescents with type 2 diabetes is of concern for both healthcare providers and payers. Among healthcare professionals, diabetic kidney disease often seems to be a topic they find both concerning and confusing. The concern seems to reflect widespread recognition that kidney disease is an important and serious complication of diabetes. However, there seems to be significant uncertainty about how the kidney disease should be managed and how it impacts other aspects of diabetes care. Anxiety around the issue of diabetes and kidney disease has the potential to result in clinical inertia, driven by a desire to avoid making mistakes. Optimal care for kidney disease requires a team that is motivated but that is also confident in its understanding of the disease. I hope that this nephropathythemed issue of Canadian Journal of Diabetes will help to add clarity for teams taking care of people with diabetes and kidney disease.
What’s in a Name? Several different names are used when talking about kidney disease, and that contributes to some of our confusion. (Figure 1). Chronic kidney disease (CKD) is a nonspecific term describing a long-term reduction in renal function that may or may not be progressive and that may be the result of several different disease processes. Although diabetes is a leading cause of CKD, the disease affects many people who do not have diabetes. Diabetic nephropathy (DN) is a more specific term describing a clinical syndrome of albuminuria, hypertension and a progressive decline in renal function that has typical appearances on kidney biopsy. DN is more common with poor glycemic control and usually develops after more than 10 years of duration of diabetes. Diabetic kidney disease (DKD) is an intermediate term that captures DN and also CKD in people with diabetes due to other causes, including hypertension and atherosclerosis. In people with longstanding type 1 diabetes and histories of albuminuria, DKD is almost invariably due to “pure” DN. In type 2 diabetes, biopsies suggest that DKD is often due to hypertensive or renovascular disease or a combination of the two plus diabetes.
defined by abnormalities in either of these aspects: reductions in the glomerular filtration rate and/or the presence of albumin in the urine. Classically, DN is defined by the presence of albuminuria followed (sometimes years) later by reduced glomerular filtration rate (GFR). Other kidney diseases, particularly renovascular disease, usually present with reduced GFR but without albuminuria. Thus, CKD can be defined based on either reduced GFR or albuminuria or both. People with CKD are at increased risk for cardiovascular disease and for end stage renal disease (ESRD), but the risks seem to be highest in people with CKD who have low GFR and albuminuria (Figure 2). It is important to remember that although albuminuria and GFR are often described as categoric variables (micro-albuminuria, macroalbuminuria, CKD stages 1 through 5), these risk factors behave as continuous variables (see Dr MacFarlane’s article in this issue). What are the Risks? Widespread reporting of estimated GFR (eGFR) derived from serum creatinine levels by diagnostic labs in Canada and around the world has increased the awareness of and anxiety about kidney function but has not necessarily improved care (1). Blood tests are often ordered during illness, when changes in fluid status and medications can cause acute changes in serum creatinine, which in turn are reflected in changes in eGFR. Our guidelines recommend that eGFR should not be used when kidney function is changing rapidly so as to assess the stage of CKD (2). This might be analogous to the advice one would give to a novice investor when seeing a 1-day drop in the price of a stock. It is important that healthcare professionals pay close attention to trends in renal status. A narrow focus looking at current GFR may lead us to overestimate risk for ESRD in an elderly person in whom the eGFR is low but stable, while underestimating the risk in a young person with dipstick-positive proteinuria and proliferative retinopathy with an eGFR of 90 mL/min but a level that has fallen by 10 mL/min over the past year. The risks for ESRD in subjects with type 1 diabetes and CKD is much higher (approximately 10 times higher) than in subjects with type 2 diabetes. Fortunately, modern therapy has seen a significant decline in the proportion of people with type 1 diabetes progressing to ESRD (to
