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Proteinuria
Proteinuria
Introduction
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:
protecting you from infection, helping your blood coagulate, and keeping 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 two proteins that are
most likely to appear in urine are albumin and globulin. Albumin is smaller and therefore
more likely to escape through the filters of the kidney, called glomeruli. 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
only albumin 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 so that kidney disease can be detected and treated 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.
Who Is at Risk?
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 progressive kidney failure. In both type 1 and type 2
diabetes, the first sign of deteriorating kidney function is the presence of small amounts
of the protein albumin in the urine, 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 25 to 44 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.
What Are the Signs of Proteinuria and Kidney Failure?
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. Alternatively, 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.
What Are the Tests for Proteinuria?
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. A more
sophisticated chemical analysis is needed to find smaller amounts (microalbuminuria). The
most dependable measure of proteinuria requires you to collect your urine for 24 hours.
You will be given a special container and instructions for starting and stopping the
collection and for storing the container.
Your doctor will also want to 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.
How Is Proteinuria Treated?
If you have diabetes, hypertension, or both, the first goal of treatment will be to
control your blood sugar and blood pressure. If you have diabetes, you should test your
blood sugar 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.
These drugs have been found to protect kidney function even more than other drugs that
provide the same level of blood pressure control.
People who have high blood pressure and proteinuria but not diabetes may also benefit
from taking an ACE inhibitor. The National Heart, Lung, and Blood Institute recommends
keeping blood pressure below 125/75 mm Hg for people with proteinuria greater than 1 gram
per 24 hours.
In addition to blood sugar 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.
Hope Through Research
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.
Points To Remember
- Proteinuria is a condition in which urine contains an abnormal amount of protein.
- 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 are older or
overweight, 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 sugar or blood pressure.
For More Information
American Kidney Fund
6110 Executive Boulevard
Suite 1010
Rockville, MD 20852
Phone: (800) 638-8299 or (301) 881-3052
Email: helpline@akfinc.org
Internet: http://www.akfinc.org/
National Kidney Foundation
30 East 33rd Street
New York, NY 10016
Phone: (800) 622-9010 or (212) 889-2210
Email: info@kidney.org
Internet: http://www.kidney.org/
National Kidney and Urologic Diseases Information Clearinghouse
3 Information Way
Bethesda, MD 20892-3580
Email: nkudic@info.niddk.nih.gov
The National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC) is a
service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).
NIDDK is part of the National Institutes of Health under the U.S. Department of Health and
Human Services. Established in 1987, the clearinghouse provides information about diseases
of the kidneys and urologic system to people with kidney and urologic disorders and to
their families, health care professionals, and the public. NKUDIC answers inquiries;
develops and distributes publications; and works closely with professional and patient
organizations and Government agencies to coordinate resources about kidney and urologic
diseases.
Publications produced by the clearinghouse are carefully reviewed for scientific
accuracy, content, and readability.
This e-text is not copyrighted. The clearinghouse encourages users of this e-pub to
duplicate and distribute as many copies as desired.
NIH Publication No. 01-4732
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