Proteinuria
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Proteinuria describes a condition in which urine contains an
abnormal amount of protein. Proteins are the building blocks for all
body parts, including muscles, bones, hair, and nails. Proteins in
your blood also perform a number of important functions. They
protect you from infection, help your blood coagulate, and keep the
right amount of fluid circulating through your body.
As blood passes through healthy kidneys, they filter the waste
products out and leave in the things the body needs, like proteins.
Most proteins are too big to pass through the kidneys' filters into
the urine unless the kidneys are damaged. The main protein that is
most likely to appear in urine is albumin. Albumin is smaller and
therefore more likely to escape through the filters of the kidney,
called glomeruli. Sometimes the term albuminuria is used when the
test detects albumin specifically. Albumin's function in the body
includes retention of fluid in the blood. It acts like a sponge,
soaking up fluid from body tissues.
Inflammation in the glomeruli is called
glomerulonephritis, or simply nephritis.
Many diseases can cause this inflammation, which leads to
proteinuria. Additional processes that can damage the glomeruli and
cause proteinuria include diabetes, hypertension, and other forms of
kidney diseases.
Research shows that the level and type of proteinuria (whether
the urinary proteins are albumin only or include other proteins)
strongly determine the extent of damage and whether you are at risk
for developing progressive kidney failure.
Proteinuria has also been shown to be associated with
cardiovascular disease. Damaged blood vessels may lead to heart
failure or stroke as well as kidney failure. If your doctor finds
that you have proteinuria, you will want to do what you can to
protect your health and prevent any of these diseases from
developing.
Several health organizations recommend that some people be
regularly checked for proteinuria to detect and treat kidney disease
before it progresses. A 1996 study sponsored by the National
Institutes of Health determined that proteinuria is the best
predictor of progressive kidney failure in people with type 2
diabetes. The American Diabetes Association recommends regular urine
testing for proteinuria for people with type 1 or type 2 diabetes.
The National Kidney Foundation recommends that routine checkups
include testing for excess protein in the urine, especially for
people in high-risk groups.
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People with diabetes, hypertension, or certain family backgrounds
are at risk for proteinuria. In the United States, diabetes is the
leading cause of end-stage renal disease (ESRD), the result of
chronic kidney disease. In both type 1 and type 2 diabetes, the
first sign of deteriorating kidney function is the presence of small
amounts of albumin in the urine, a condition called
microalbuminuria. As kidney function declines, the
amount of albumin in the urine increases, and microalbuminuria
becomes full-fledged proteinuria.
High blood pressure is the second leading cause of ESRD.
Proteinuria in people with high blood pressure is an indicator of
declining kidney function. If the hypertension is not controlled,
the person can progress to full renal failure.
African Americans are more likely than white Americans to have
high blood pressure and to develop kidney problems from it, even
when their blood pressure is only mildly elevated. In fact, African
Americans ages 20 to 49 are 20 times more likely than their white
counterparts to develop hypertension-related kidney failure. High
blood pressure is the leading cause of kidney failure among African
Americans.
Other groups at risk for proteinuria are American Indians,
Hispanic Americans, Pacific Islander Americans, older people, and
overweight people. People who have a family history of kidney
disease should also have their urine tested regularly.
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Large amounts of protein in your urine may cause it to look foamy
in the toilet. Also, because the protein has left your body, your
blood can no longer soak up enough fluid and you may notice swelling
in your hands, feet, abdomen, or face. These are signs of very large
protein loss. More commonly, you may have proteinuria without
noticing any signs or symptoms. Testing is the only way to
find out how much protein you have in your urine.
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| Containers for collecting
urine | |
To test for proteinuria, you will need to give a urine sample. A
strip of chemically treated paper will change color when dipped in
urine that has too much protein. More sensitive tests for protein or
albumin in the urine are recommended for people at risk for kidney
disease, especially those with diabetes. The protein-to-creatinine
or albumin-to-creatinine ratio can be measured on a sample of urine
to detect smaller amounts of protein, which can indicate kidney
disease. If the laboratory test shows high levels of protein,
another test should be done 1 to 2 weeks later. If the second test
also shows high levels of protein, you have persistent proteinuria
and should have additional tests to evaluate your kidney
function.
Your doctor will also test a sample of your blood for creatinine
and urea nitrogen. These are waste products that healthy kidneys
remove from the blood. High levels of creatinine and urea nitrogen
in your blood indicate that kidney function is impaired.
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If you have diabetes, hypertension, or both, the first goal of
treatment will be to control your blood glucose and blood pressure.
If you have diabetes, you should test your blood glucose often,
follow a healthy eating plan, take your medicines, and get plenty of
exercise. If you have diabetes and high blood pressure, your doctor
may prescribe a medicine from a class of drugs called ACE
(angiotensin-converting enzyme) inhibitors or angiotensin receptor
blockers (ARB). These drugs have been found to protect kidney
function even more than other drugs that provide the same level of
blood pressure control. The American Diabetes Association recommends
that people with diabetes keep their blood pressure below 130/80.
People who have high blood pressure and proteinuria but not
diabetes may also benefit from taking an ACE inhibitor or ARB. Their
blood pressure should be maintained below 130/80.
In addition to blood glucose and blood pressure control, the
National Kidney Foundation recommends restricting dietary salt and
protein. Your doctor may refer you to a dietitian to help you follow
a healthy eating plan.
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In recent years, researchers have learned much about kidney
disease. The National Institute of Diabetes and Digestive and Kidney
Diseases (NIDDK) sponsors several programs aimed at understanding
kidney failure and finding treatments to stop its progression.
NIDDK's Division of Kidney, Urologic, and Hematologic Diseases
(DKUHD) supports basic research into normal kidney function and the
diseases that impair normal function at the cellular and molecular
levels, including diabetes, high blood pressure, glomerulonephritis,
and other diseases marked by proteinuria.
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- Proteinuria is a condition in which urine contains an abnormal
amount of protein.
- The term albuminuria is also often used because some tests
measure this protein specifically and it is the major type of
protein in the urine.
- Proteinuria may be a sign that your kidneys are damaged and
that you are at risk for end-stage renal disease.
- Several health organizations recommend that people be
regularly checked for proteinuria so that kidney disease can be
detected and treated before it progresses.
- Groups at risk for proteinuria and kidney failure include
African Americans, American Indians, Hispanic Americans, Pacific
Islander Americans, people who have diabetes or hypertension, and
people who have a family history of kidney disease.
- You may have proteinuria without noticing any signs or
symptoms. Testing is the only way to find out how much protein you
have in your urine.
- If you have diabetes or hypertension, or both, the first goal
of treatment will be to control your blood glucose and blood
pressure.
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American Kidney Fund
National Kidney Foundation
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