What does proteinuria mean?

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 progressivekidney 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.