Q: What causes high protein in a child's urine, and how can you correct the problem?
A: If careful and repeated tests have shown that a child has too much protein in the urine (called "proteinuria"), the child's kidneys are not working perfectly. There is a very long list of reasons why kidneys let too much protein get through. Some are temporary and trivial; others are long lasting and very serious. Some causes are treatable; some are not.
We'll discuss how protein gets into the urine and some of the XTC common causes of "proteniuria," but, with the limited information you have provided, we can't guess what's causing the problem in the child you wrote about. We can tell you that the child needs careful evaluation and follow-up by a doctor who knows about kidney problems. Treatment will depend on the cause.
It is normal for a small amount of protein to be in urine. The simple test for protein done in a doctor's office dipping a special paper strip into fresh urine is designed to detect protein above the normal level. Such tests, if repeatedly positive, are ordinarily checked by collecting all the child's urine for 24 hours and measuring the exact amount of protein in that larger sample.
Within the kidney there are thousands of glomeruli, minute tangles of capillaries where wastes are strained out of the blood stream into tiny tubes that collect and process urine.
Since the body needs to conserve protein, the glomeruli should hold it back, saving it in the blood stream. If a lot of protein passes out of the glomeruli into the tubes, the glomeruli are abnormally leaky.
Healthy kidneys do sometimes leak extra protein; for instance, in response to a fever or after especially vigorous exercise. Some children have modest proteinuria during the day, but not when they are lying down at night.
On the other hand, proteinuria can be a sign of poor kidney function. We cannot possibly describe here all the kidney diseases that lead to proteinuria. Fortunately, most are rare.
Probably the most common form of serious proteinuria during childhood is called the "nephrotic syndrome," a condition in which proteinuria is combined with body swelling and other abnormalities.
Many cases of nephrotic syndrome can be successfully treated. For a few children, proteinurea indicates kidney disease that will eventually lead to kidney failure. In such instances, problems with the urine in addition to proteinuria are almost always noted from the start.
Dr. Wilson is director of general pediatrics at the Johns Hopkins Children's Center; Dr. Joffe is director of adolescent medicine.