Diabetes and Kidney Disease: Understanding the Kidneys

The kidneys act as filters to clean the blood. They get rid of waste and extra fluid. The tiny filters throughout the kidneys are called glomeruli.

When kidneys are healthy, the arteries brings blood and waste from the bloodstream into the kidney. The glomeruli clean the blood. Then waste and extra fluid go out into the urine through the ureter. Clean blood goes out of the kidney and back into the bloodstream through the veins.

Diabetes and Kidney Disease: 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 kidney 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.

Diabetes and Kidney Disease: The Effects of High Blood Pressure

Diabetes and Kidney Disease: An Overview Preventing and Slowing Kidney Disease Dialysis and Transplantation

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 in people who already have it.

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. 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.

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
* Nerves.

Helpful Tips Regarding Diabetes and Kidney Disease
If you have diabetes. consider the following suggestions:

* Have your doctor measure your hemoglobin A1c level at least twice a year. The test provides a weighted average of your blood glucose level for the previous three months. Aim to keep it at less than 7 percent.

* Work with your doctor regarding insulin injections, medicines, meal planning, physical activity, and blood glucose monitoring.

* Have your blood pressure checked several times a year. If blood pressure is high, follow your doctor’s plan for keeping it near normal levels. Aim to keep it at less than 130/80.

* Ask your doctor whether you might benefit from taking an ACE inhibitor or ARB.

* Have your urine checked annually for microalbumin and protein. If there is protein in your urine, have your blood checked for elevated amounts of waste products, such as creatinine. The doctor should provide you with an estimate of your kidney’s filtration based on the blood creatinine level.

* Ask your doctor whether you should reduce the amount of protein in your diet. Ask for a referral to see a registered dietitian to help you with meal planning.

Statistics Regarding Diabetes and Kidney Disease

Diabetes and Kidney Disease: An Overview Preventing and Slowing Kidney Disease Dialysis and Transplantation

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 over 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
* Transplantation to receive a healthy donor kidney.

Most Americans 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
* 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.

While both types of diabetes can lead to kidney disease. type 1 diabetes is more likely to lead to kidney failure. Twenty percent to 40 percent of people with type 1 diabetes develop kidney failure by the age of 50. Some develop kidney failure before the age of 30. Between 1993 and 1997, more than 100,000 people in the United States were treated for kidney failure caused by type 2 diabetes.

* Using certain types of blood pressure medicine
* Eating a moderate-protein diet
* Intensive management of blood glucose.

An example of an effective ARB is losartan, which has also been shown to protect kidney function and lower the risk of cardiovascular events (such as a stroke or heart attack). Another example of an ARB used to treat diabetic nephropathy is irbesartan.

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 blood pressure medication have proven effective in slowing the progression of kidney disease:

* Angiotensin-converting enzyme inhibitors (ACE inhibitors)
* Angiotensin II receptor blockers (ARBs).

Many people require two or more drugs to control their blood pressure. In addition to an ACE inhibitor or an ARB, a diuretic is useful. Other drugs may also be needed, such as:

* Beta blockers
* Calcium channel blockers
* Other high blood pressure medications.

Moderate-Protein Diets

In people with diabetes, excessive consumption of protein may be harmful. Experts recommend that people with kidney disease caused by 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

Diabetes and Kidney Disease: An Overview Preventing and Slowing Kidney Disease Dialysis and Transplantation

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
* Consulting a healthcare team frequently.

Some people use an insulin pump to supply insulin throughout the day.

A number of studies have pointed to the beneficial effects of intensive management. One study involved 1,441 participants who had type 1 diabetes. Researchers found a 50 percent decrease in both development and progression of early diabetic kidney disease in participants who followed an intensive regimen for controlling blood glucose levels. The intensively managed patients had average blood glucose levels of 150 milligrams per deciliter — about 80 milligrams per deciliter lower than the levels observed in the conventionally managed patients.