Am Fam Physician. 1998;58(5):1158-1159
See related article on proteinuria.
Proteins are essential in our bodies. Normally, proteins move around in our blood, carrying food, hormones and medicine to all parts of the body. They also help keep water inside tiny blood vessels.
What is proteinuria?
Proteinuria is the name of a medical condition. It means protein is in the urine. As blood moves through the kidneys, the kidneys filter out waste products, excess fluid and salts. The clean blood cycles back through the body. Most proteins are too big to go through the kidneys, so usually no protein is found in urine. If your doctor finds protein in your child's urine, that means your child's kidney filters may not be working as they should—possibly because of inflammation (swelling). Sometimes infection or toxic chemicals damage the kidneys, and this makes protein show up in the urine.
Dipping a special strip of paper into a sample of urine tells your doctor if protein is in it. If only a little protein is in the urine, your child probably has a benign (harmless) condition (such as orthostatic proteinuria—see below). Your doctor might do a few other tests to make sure.
Your doctor will ask you to collect a 24-hour urine sample from your child. Directions for doing this are at the end of this handout. A 24-hour urine collection lets your doctor measure the protein in the urine. This test helps show how well your child's kidneys are working. Your doctor may also do some blood tests.
If a lot of protein is found in your child's urine, a more serious kidney disease might be the problem. Proteinuria doesn't cause pain. But when a lot of protein is in the urine, the level of protein in the blood may go down. This can cause swelling in your child's eyelids, ankles and legs. High blood pressure is another sign of this problem.
What is orthostatic proteinuria?
Orthostatic proteinuria occurs in some older children and teenagers. The word orthostatic means “upright.” The condition is called “orthostatic proteinuria” because protein goes into the urine only when the child is in the upright position (standing up).
Children with this condition have no kidney damage but, for some unknown reason, they lose protein into the urine during the day when they are active. At night, while they sleep, their kidneys don't let any protein into the urine. Your doctor diagnoses this harmless condition by checking two urine samples. The first one is collected in the morning, right after your child gets up, and it's kept in one container. The second sample is collected during the day (all the urine collected during the day is put in the second container). If your child has orthostatic proteinuria, the morning sample won't have protein in it. The urine collected during the day will have protein in it.
How is proteinuria treated?
If your child has orthostatic proteinuria or only small amounts of protein in the urine, no treatment is needed. Sometimes your doctor will check your child's urine again after a few months. Your doctor wants to see if the amount of protein in the urine goes down. If the amount of protein in the urine doesn't change or if there is more protein, your doctor will send you and your child to a kidney specialist (called a nephrologist—say: neff-rollo-gist). The nephrologist may perform a kidney biopsy. (A small piece of kidney tissue is taken out, using a needle. The kidney tissue is looked at under a microscope.) When your doctor finds out what causes the protein in your child's urine, he or she can find the best way to treat the problem.
No matter what caused the kidney problem, a few simple things can help your child. Eating less salt can reduce the swelling. Medicine can control the inflammation (swelling) of the kidneys that may be causing protein to get into the urine. The medicine is usually given in a high dose at first, and in a lower dose later on. Some children take a low dose of medicine for months, or even years. It's important to follow your doctor's instructions about taking the medicine. It's also important to visit the doctor for regular checkups.
Do I need to restrict my child's activities?
No. Although protein in the urine can increase during exercise, this won't hurt your child's kidneys. So you don't need to restrict your child's activities.
How do I do a 24-hour urine collection?
In children who are potty-trained, you should start the collection on a day when your child doesn't go to school, usually on a Sunday. As soon as your child gets out of bed in the morning, have him or her urinate into the toilet. This urine is not saved; just flush it down the toilet. Write down the exact time your child urinates. (Children who aren't potty-trained usually go in the hospital for this test.)
After this, whenever your child needs to urinate, have your child urinate in the special container the doctor or the laboratory gives you. For girls, collect the urine first in a urine “hat,” then pour it into the special container. You don't need to mark the times when these urine samples are collected.
It's important to collect all the urine your child produces all day and in the night. The next morning, wake your child up at about the same time as you did the day before. Have your child urinate into the container one last time. This ends the 24-hour collection. Now write the date and the time on the container label. Bring the container to the laboratory on this day. Since bacteria can grow in urine at room temperature, it's important to keep the urine container in a refrigerator during the collection and before you deliver it to the laboratory. Be sure to wash your hands after handling the container.