Proteinuria

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.

source: http://kidney.niddk.nih.gov/kudiseases/pubs/proteinuria/index.htm