Proteinuria

Proteinuria describes a condition in which urine contains an abnormal amount of protein. A major protein in the blood is called albumin, which acts like a sponge, drawing extra fluid from the body into the bloodstream, where it remains until the kidneys remove it. But when albumin leaks into the urine, the blood loses its capacity to absorb extra fluid from the body. Fluid can accumulate outside the circulatory system in the face, hands, feet, or ankles and cause swelling.

Symptoms and Diagnosis

Large amounts of protein in your urine may cause it to look foamy in the toilet. Also, because the protein albumin 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.

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. Laboratory tests that measure exact amounts of 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.

Causes

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 (called glomeruli) into the urine unless the filters are damaged. 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.

Treatment

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 a similar class called ARBs (angiotensin receptor blockers). 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 also benefit from taking an ACE inhibitor or ARB. Their blood pressure should be maintained below 130/80. To maintain this target, you may need to take a combination of two or more blood pressure medicines. Your doctor may also prescribe a diuretic in addition to your ACE inhibitor or ARB. Diuretics are also called "water pills" because they help you urinate and get rid of excess fluid in your body.

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 develop and follow a healthy eating plan.

Reference:

National Kidney and Urologic Diseases Information Clearinghouse, USA.