Pediatric Nephrology Clinical Services : Conditions & Procedures

Proteinuria

Proteinuria—also called albuminuria or urine albumin—is a condition in which urine contains an abnormal amount of protein. Albumin is the main protein in the blood. Proteins are the building blocks for all body parts, including muscles, bones, hair, and nails. 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.

Who is at risk for proteinuria?

People with diabetes, hypertension or certain family backgrounds are at risk for proteinuria. In the United States, diabetes is the leading cause of ESRD. In both type 1 and type 2 diabetes, albumin in the urine is one of the first signs of deteriorating kidney function. As kidney function declines, the amount of albumin in the urine increases.

Another risk factor for developing proteinuria is hypertension, or 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. 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.

What are the signs and symptoms of proteinuria?

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.

What are the tests for proteinuria?

A urine test will compare the amount of albumin in the urine sample with the amount of creatinine, a waste product of normal muscle breakdown.

What should a person with proteinuria do?

If a child has diabetes, hypertension, or both, the first goal of treatment will be to control blood glucose, also called blood sugar, and blood pressure. People with diabetes should test their blood glucose often, follow a healthy eating plan, take prescribed medicines, and get the amount of exercise recommended by their doctor.

In addition to blood glucose and blood pressure control, the National Kidney Foundation recommends restricting dietary salt and protein. A doctor may refer a patient to a dietitian to help develop and follow a healthy eating plan.