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Kidney Disease of Diabetes
Each year in the United States, nearly 100,000 people are diagnosed with kidney failure, a serious condition in which the kidneys fail to rid the body of wastes. Kidney failure is the final stage of a slow deterioration of the kidneys, a process known as nephropathy.Diabetes is the most common cause of kidney failure, accounting for more than 40 percent of new cases. Even when drugs and diet are able to control diabetes, the disease can lead to nephropathy and kidney failure. Most people with diabetes do not develop nephropathy that is severe enough to cause kidney failure. About 17 million people in the United States have diabetes, and more than 100,000 people are living with kidney failure as a result of diabetes. People with kidney failure undergo either dialysis, which substitutes for some of the filtering functions of the kidneys, or transplantation to receive a healthy donor kidney. Most U.S. citizens who develop kidney failure are eligible for federally funded care. In 2000, care for patients with kidney failure cost the nation nearly $20 billion. African Americans, American Indians and Hispanic Americans develop diabetes, nephropathy and kidney failure at rates higher than average. Scientists have not been able to explain these higher rates. Nor can they explain fully the interplay of factors leading to diabetic nephropathy — factors including heredity, diet and other medical conditions, such as high blood pressure. They have found that high blood pressure and high levels of blood glucose increase the risk that a person with diabetes will progress to kidney failure. Two Types of Diabetes There are two types of diabetes. In patients with either type, the body does not properly process and use food. The human body normally converts food to glucose, the simple sugar that is the main source of energy for the body's cells. To enter cells, glucose needs the help of insulin, a hormone produced by the pancreas. When a person does not make enough insulin, or the body does not respond to the insulin that is present, the body cannot process glucose, and it builds up in the bloodstream. High levels of glucose in the blood lead to a diagnosis of diabetes. Both types of diabetes can lead to kidney disease. Type 1 Diabetes Only about one in 20 people with diabetes has type 1 diabetes, which tends to occur in young adults and children. Type 1 used to be known as insulin-dependent diabetes mellitus (IDDM) or juvenile diabetes. In type 1 diabetes, the body stops producing insulin. People with type 1 diabetes must take daily insulin injections or use an insulin pump. They also control blood glucose levels with meal planning and physical activity. Type 1 diabetes is more likely to lead to kidney failure. By the age of 50, 20 percent to 40 percent of people with type 1 diabetes develop kidney failure. Some develop kidney failure before the age of 30. Type 2 Diabetes About 95 percent of people with diabetes have type 2 diabetes, once known as noninsulin-dependent diabetes mellitus (NIDDM) or adult-onset diabetes. Many people with type 2 diabetes do not respond normally to their own or to injected insulin — a condition called insulin resistance. Type 2 diabetes occurs more often in people over the age of 40, and many people with type 2 are overweight. Many also are not aware that they have the disease. Some people with type 2 control their blood glucose with meal planning and physical activity. Others must take pills that stimulate production of insulin, reduce insulin resistance, decrease the liver's output of glucose, or slow absorption of carbohydrate from the gastrointestinal tract. Still others require injections of insulin. Between 1993 and 1997, more than 100,000 people in the United States were treated for kidney failure caused by type 2 diabetes. The Course of Kidney Disease Diabetic kidney disease takes many years to develop. In some people, the filtering function of the kidneys is actually higher than normal in the first few years of their diabetes. This process has been called hyperfiltration. Over several years, people who are developing kidney disease will have small amounts of the blood protein albumin begin to leak into their urine. At its first stage, this condition has been called microalbuminuria. The kidney's filtration function usually remains normal during this period. As the disease progresses, more albumin leaks into the urine. Various names are attached to this interval of the disease, such as overt diabetic nephropathy or macroalbuminuria. As the amount of albumin in the urine increases, filtering function usually begins to drop. The body retains various wastes as filtration falls. Creatinine is one such waste, and a blood test for creatinine can measure the decline in kidney filtration. As kidney damage develops, blood pressure often rises as well. Overall, kidney damage rarely occurs in the first 10 years of diabetes, and usually 15 to 25 years will pass before kidney failure occurs. For people who live with diabetes for more than 25 years without any signs of kidney failure, the risk of ever developing it decreases. Effects of High Blood Pressure High blood pressure, or hypertension, is a major factor in the development of kidney problems in people with diabetes. Both a family history of hypertension and the presence of hypertension appear to increase chances of developing kidney disease. Hypertension also accelerates the progress of kidney disease where it already exists. In the past, hypertension was defined as blood pressure exceeding 140 millimeters of mercury-systolic and 90 millimeters of mercury-diastolic. Professionals shorten the name of this limit to 140/90 or "140 over 90." The terms systolic and diastolic refer to pressure in the arteries during contraction of the heart (systolic) and between heartbeats (diastolic). The American Diabetes Association and the National Heart, Lung, and Blood Institute recommend that people with diabetes keep their blood pressure below 130/80. Hypertension can be seen not only as a cause of kidney disease, but also as a result of damage created by the disease. As kidney disease proceeds, physical changes in the kidneys lead to increased blood pressure. Therefore, a dangerous spiral, involving rising blood pressure and factors that raise blood pressure, occurs. Early detection and treatment of even mild hypertension are essential for people with diabetes. Preventing and Slowing Kidney Disease Blood Pressure Medicines Scientists have made great progress in developing methods that slow the onset and progression of kidney disease in people with diabetes. Drugs used to lower blood pressure (antihypertensive drugs) can slow the progression of kidney disease significantly. Two types of drugs, angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs), have proven effective in slowing the progression of kidney disease. Many people require two or more drugs to control their blood pressure. In addition to an ACE inhibitor or an ARB, a diuretic is very useful. Beta blockers, calcium channel blockers, and other blood pressure drugs also may be needed. An example of an effective ACE inhibitor is captopril, which doctors commonly prescribe for treating kidney disease of diabetes. The benefits of captopril extend beyond its ability to lower blood pressure: it may directly protect the kidney's glomeruli. ACE inhibitors have lowered proteinuria and slowed deterioration even in diabetic patients who did not have high blood pressure. An example of an effective ARB is losartan, which has also been shown to protect kidney function and lower the risk of cardiovascular events. Any medicine that helps patients achieve a blood pressure target of 130/80 or lower provides benefits. Patients with even mild hypertension or persistent microalbuminuria should consult a physician about the use of antihypertensive medicines. Moderate-Protein Diets In people with diabetes, excessive consumption of protein may be harmful. Experts recommend that people with kidney disease of diabetes consume the recommended dietary allowance (RDA) for protein, but avoid high-protein diets. For people with greatly reduced kidney function, a diet containing reduced amounts of protein may help delay the onset of kidney failure. Anyone following a reduced-protein diet should work with a dietitian to ensure adequate nutrition. Intensive Management of Blood Glucose Antihypertensive drugs and low-protein diets can slow kidney disease when significant nephropathy is present. A third treatment, known as intensive management of blood glucose or glycemic control, has shown great promise for people with type 1 and type 2 diabetes, especially for those in early stages of nephropathy. Intensive management is a treatment regimen that aims to keep blood glucose levels close to normal. The regimen includes testing blood glucose frequently, administering insulin frequently throughout the day on the basis of food intake and exercise, following a diet and exercise plan, and consulting a health care team frequently. Some people use an insulin pump to supply insulin throughout the day. Dialysis and Transplantation When people with diabetes experience kidney failure, they must undergo either dialysis or a kidney transplant. As recently as the 1970s, medical experts commonly excluded people with diabetes from dialysis and transplantation, in part because the experts felt damage caused by diabetes would offset benefits of the treatments. Today, because of better control of diabetes and improved rates of survival following treatment, doctors do not hesitate to offer dialysis and kidney transplantation to people with diabetes. Currently, the survival of kidneys transplanted into patients with diabetes is about the same as survival of transplants in people without diabetes. Dialysis for people with diabetes also works well in the short run. Even so, people with diabetes who receive transplants or dialysis experience higher morbidity and mortality because of coexisting complications of the diabetes, such as damage to the heart, eyes and nerves. Good Care Makes a Difference If you have diabetes:
Source: National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health Related Article | |
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