Proteinuria is a condition in which urine contains a detectable amount of protein. Proteinuria is a sign of chronic kidney disease (CKD).
Proteins in the blood also perform a number of important functions. They protect the body from infection, help blood clot, and keep the right amount of fluid circulating throughout the body.
As blood passes through healthy kidneys, they filter out the waste products and leave in the things the body needs, like albumin and other proteins. Most proteins are too big to pass through the kidneys' filters into the urine. However, proteins from the blood can leak into the urine when the filters of the kidney, called glomeruli, are damaged.
Proteinuria is a sign of chronic kidney disease (CKD), which can result from diabetes, high blood pressure, and diseases that cause inflammation in the kidneys. For this reason, testing for albumin in the urine is part of a routine medical assessment for everyone. Kidney disease is sometimes called renal disease. If CKD progresses, it can lead to end-stage renal disease (ESRD), when the kidneys fail completely. A person with ESRD must receive a kidney transplant or regular blood-cleansing treatments called dialysis.
People with diabetes, hypertension, or certain family backgrounds are at risk for proteinuria. 1 In both type 1 and type 2 diabetes, protein in the urine is one of the first signs of deteriorating kidney function. As kidney function declines, the amount of protein in the urine increases.
Another risk factor for developing proteinuria is high blood pressure. Proteinuria in a person with high blood pressure is an indicator of declining kidney function. If the hypertension is not controlled, the person can progress to full kidney failure.
African Americans are more likely than Caucasians 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 are six times more likely than Caucasians to develop hypertension-related kidney failure.2
Other groups at risk for proteinuria are American Indians, Hispanics/Latinos, Pacific Islander Americans, older adults, and overweight people. These at-risk groups and people who have a family history of kidney disease should have their urine tested regularly.
Proteinuria has no signs or symptoms in the early stages. Large amounts of protein in the urine may cause it to look foamy in the toilet. Also, because protein has left the body, the blood can no longer soak up enough fluid, so swelling in the hands, feet, abdomen, or face may occur. This swelling is called edema. These are signs of large protein loss and indicate that kidney disease has progressed. Laboratory testing is the only way to find out whether protein is in a person’s urine before extensive kidney damage occurs.
The National Kidney Foundation recommends that routine checkups include testing for excess protein in the urine, especially for people in high-risk groups.
Researchers have found that a single urine sample can provide the needed information. If the a second test also shows high levels of protein, the person has persistent proteinuria, a sign of declining kidney function, and should have additional tests to evaluate kidney function.