A child’s urine sometimes can contain abnormally high amounts of protein. Although the body needs proteins to perform essential functions, such as guarding against infections and helping the blood to clot, protein detected in the urine may mean that the kidneys are not working properly and are allowing proteins (which are large molecules) to leak out into the urine. This may be due to inflammation of the kidney’s filtering membranes, allowing this leakage to occur.
Proteinuria often causes no symptoms. But when high levels of protein are in the urine, blood protein levels may drop and your child could develop swelling in the legs, ankles, abdomen, or eyelids. Blood pressure may be elevated. If your pediatrician suspects proteinuria, she can use a simple test in which a chemically treated paper strip is dipped into the urine, and will change colors if protein is present. She may recommend that you collect urine samples from your child just after awakening in the morning, and that the urine specimens be examined in the laboratory, or that your child have some blood tests. In some children, a small amount of protein may be found in the urine for a short time and later disappear without any consequences. At times, your pediatrician may decide to have your child seen by a kidney specialist (nephrologist), who might recommend performing a kidney biopsy to help decide what may be causing the problem.
During a kidney biopsy, a needle is used to remove a small amount of kidney tissue for examination in the laboratory. Your child will be sedated for this procedure and the area over the kidney will be made numb by injecting a local anesthetic.
Medication can be given to treat some underlying kidney problems associated with proteinuria. Your pediatrician might recommend that your child consume less salt to curtail the swelling associated with proteinuria. Children who have had proteinuria, even if it appears to be one of the harmless varieties, probably will be monitored over time with regular urine tests.