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.
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
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.
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.
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.
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
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
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.