Proteinuria in Children

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What is proteinuria?

Proteinuria is when protein is found in the urine. The job of the kidneys is to filter out waste, extra fluid, and salt. These wastes leave the body in urine and usually only a small amount of protein is found in urine because most proteins are too big to be filtered through the kidneys.

If your doctor finds protein in your child’s urine, it means your child’s kidneys may not be working as they should, possibly because of inflammation (swelling). Sometimes infection or chemicals damage the kidneys, and this makes protein show up in the urine. If your child has an infection, the proteinuria will go away once the infection is treated.

Proteinuria doesn’t cause pain. 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.

How is proteinuria diagnosed?

Your doctor may want to recheck your child’s urine for protein because it will often go away on its own (transient proteinuria). If it is still high, your doctor may 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 amount of protein in the urine more accurately. Your doctor may also do some blood tests.

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 standing up.

Children who have 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 2 urine samples. The first is collected in the morning, right after your child gets up. The second sample is collected throughout the day. The samples are kept in separate containers. If your child has orthostatic proteinuria, the morning sample won’t have protein in it, but 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. If there is a large amount of protein in your child’s urine and your child has swelling of the legs and eyelids, your doctor may send your child to a kidney specialist (called a nephrologist). The nephrologist may perform a kidney biopsy. A small piece of kidney tissue is taken out using a needle, and looked at under a microscope. When your doctor finds out what causes the protein in your child’s urine, he or she can treat the problem.

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 limit 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. Flush it down the toilet. Write down the exact time your child urinates.

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, first collect the urine in a urine “hat” (a specimen collection device), and then pour it into the special container. You don’t need to mark the times when these urine samples are collected. Be sure to wash your hands after handling the container.

It’s important to collect all the urine your child produces all day and 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 lab 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 lab.