DIABETES AND KIDNEY DISEASE 

Kidneys are remarkable organs. Inside them are millions of tiny blood vessels that act as filters. Their job is to remove waste products from the blood.   But sometimes this filtering system breaks down. Failing kidneys lose their ability to filter out waste products. One cause of kidney failure is diabetes.

Why Diabetes Damages Kidneys

When our bodies digest the protein we eat, the process creates waste products that build up in the blood. In the kidneys, millions of tiny blood vessels (capillaries) with even tinier holes in them act as filters. As blood flows through the blood vessels, small molecules such as waste products squeeze through the holes. These waste products become part of the urine. Useful substances, such as protein and red blood cells, are too big to pass through the holes in the filter. They stay where they belong—in the blood.

Diabetes can damage this system. High levels of glucose make the kidneys filter too much blood. All this extra work is hard on the filters. After many years, they start to leak. Useful protein is lost in the urine. Having small amounts of protein in the urine is called microalbuminuria. Having larger amounts is called proteinuria or macroalbuminuria.

In time, the stress of overwork causes some filters to collapse. This collapse makes more work for the remaining filters and they, too, begin collapsing. As the capillaries lose their filtering ability, waste products start to build up in the blood.

Finally, the kidneys fail. This failure is called end-stage renal disease (ESRD). ESRD is very serious. A person with ESRD needs either to have a kidney transplant or to have the blood filtered by machine (dialysis).

Who Gets Kidney Disease

Not everyone with diabetes develops kidney disease. Factors that can influence development include genetics, blood glucose control, and blood pressure.

The better a person keeps diabetes under control, the lower the chance of getting kidney disease. High blood pressure should also be kept under control. The healthier the blood pressure, the healthier the kidneys will be.

More than 30 percent of people with type 1 diabetes will one day have kidney disease, compared with perhaps 10 percent of people with type 2 diabetes. People with type 1 diabetes have 15 times the risk of ESRD as those with type 2 diabetes. The longer a person has diabetes, the higher the risk of kidney disease—up to a point. After 40 years with diabetes, if a person does not yet have kidney disease, he or she probably never will. Men are 50 percent more likely to get kidney disease than women. Most people who get diabetic kidney disease also have diabetic eye problems.

Symptoms and Diagnosis

The kidneys work so hard to make up for the failing capillaries that kidney disease produces no symptoms until almost all function is gone. Also, the symptoms are not specific. The first symptom is often fluid buildup. Others include loss of sleep, tiredness, poor appetite, upset stomach, vomiting, weakness, and difficulty concentrating.

It is vital to see a doctor regularly. The doctor can test the urine for protein, check whether blood pressure is high, and detect diabetic eye problems.

Prevention

Diabetic kidney disease can be prevented by tight blood glucose control. In the Diabetes Control and Complications Trial, tight control reduced the risk of microalbuminuria by a third. In people who already had microalbuminuria, the risk of progressing to proteinuria was about half in people on tight control. Other studies have suggested that tight control can reverse microalbuminuria.

Treatments for Kidney Disease

When kidney disease is diagnosed early (during microalbuminuria), several treatments may keep it from getting worse. When kidney disease is caught later (during proteinuria), ESRD almost always follows. Treatment at this stage can only delay the inevitable.

1. Good blood glucose control. One important treatment is tight blood glucose control.

2. Good blood pressure control. Another important treatment is tight control of blood pressure. Blood pressure has a dramatic effect on the rate at which the disease progresses. Even a mild rise in blood pressure can quickly make the disease worsen. Three ways to bring blood pressure down are losing weight, eating less salt, and avoiding alcohol and tobacco, and if necessary taking medications.

3. Special kidney–protecting drugs. ACE inhibitors are good drugs to use to protect the kidneys. Recent studies suggest that these drugs—which include captopril, enalapril, Coversyl, ramipril—slow kidney disease in addition to lowering blood pressure. In fact, these drugs are helpful even in people who do not have high blood pressure. Other drugs belonging to a new class called ARBs (Cozaar, Hyzaar, Aprovel) are equally effective.

4. Low protein diet. Another treatment some doctors use is a low-protein diet. Protein seems to increase how hard the kidneys must work. A low-protein diet can decrease protein loss in the urine and increase protein levels in the blood. Never start a low-protein diet without talking to your doctor first.

Once kidneys fail, these treatments are no longer useful. Dialysis is then necessary. The person must choose whether to continue with dialysis or to get a kidney transplant. This choice should be made as a team effort. The team should include the doctor and diabetes educator, a nephrologist (kidney doctor), a kidney transplant surgeon, a social worker, and a psychologist.