Your child’s doctor can diagnose (identify) proteinuria with a urine test. Because proteinuria may not have symptoms, it is often found with urine tests done for other reasons. Your child may need other tests. Your doctor may talk to you or your child about his or her symptoms and any medicines that he or she takes, and examine your child. Your doctor or nurse will check your child’s blood pressure to find out whether it is in a healthy range.
Urine tests
You, or a nurse, will need to collect some of your child’s urine in a small, clean container for a urine test. A dipstick will be dipped into the urine – this is a strip with chemical pads that change colour depending on what substances are in the urine. This shows whether there is protein in the urine. If the first urine test shows protein in your child’s urine, your doctor may arrange for more urine tests. Many children have a little protein in their urine occasionally – testing the urine again will confirm whether your child continues to have protein in their urine. You will need to collect samples of your child’s first morning urine, the urine passed when they first wake up in the morning.
The samples may also be sent to a laboratory for more accurate tests, such as measuring the amount of protein.
Testing urine at home
You may need to test your child’s urine at home to find out whether the proteinuria is still present. You will need to collect a sample of your child’s urine each morning, and test it with a dipstick. Your doctor or nurse will give you some equipment and show you what to do.
Urine test – 24-hour sample
A small number of children need their urine collected over a whole day and night. This can give a more accurate measurement of how much protein is being leaked.
Urine test for infections
Because proteinuria can happen with urinary tract infections, your child’s urine may need to be tested to find out whether there is an infection. The test is called a urine culture.
More about urine and blood tests
Urine tests: measuring the amount of protein
The dipstick urine test will show if there is any protein in the urine, but it does not give an accurate measurement.
The following tests are done in a laboratory.
- The urine protein:creatinine ratio (PCR) compares the amounts of protein and creatinine in the urine. Creatinine is made all the time by muscles and normally removed by the kidneys in urine.
- The albumin:creatinine ratio (ACR) compares the amounts of albumin and creatinine in the urine.
Defining proteinuria
Proteinuria is defined as PCR of more than 50 mg/mmol.(This may be slightly different in different laboratories.)
Nephrotic range proteinuria is defined as PCR more than 200 mg/mmol. This means that a lot of protein is leaked into the urine, and so there is less protein in the blood.
Blood tests: infection and the immune system
In blood tests, a small amount of blood may be taken from a vein, with a needle and syringe. Special gel or cream can be used to help your child stop feeling any pain.
The blood test results can give the doctor more information, including:
- whether your child has had a recent infection
- how well the kidneys are working – this is called the kidney function
- the amount of protein in the blood – because the kidneys leak protein into urine in proteinuria, this is sometimes enough to affect how much protein is in the blood.
- A blood test can check whether there are any antibodies – the body’s immune system makes these special proteins to identify and kill specific germs. This gives information about whether there has been an infection, and sometimes which germ caused it.
How well the kidneys are working
Urea and creatinine are chemicals that are made in the body. They are waste products and are normally removed by the kidneys into urine. In severe proteinuria, these may build up in the blood.
The kidney function can be measured with the glomerular filtration rate (GFR). The GFR is the amount of fluid (liquid) the kidneys filter each minute. It can be estimated by measuring the amount of creatinine in the blood.
Protein in the blood
Children with proteinuria lose protein in their urine. Some children lose a lot of protein, which means there is less protein in their blood. Albumin is one type of protein in the blood – because it is small, albumin is more likely to leak through the glomeruli.
Other chemicals
Electrolytes are important chemicals in the body. We need the right balance of these to stay healthy. Some important electrolytes include the following:
- sodium helps balance the amount of water in the body
- potassium is needed for the muscles, including the heart muscle, to work properly
- bicarbonate balances the amount of acid in our body, or the pH balance (also called the acid–base balance)
- phosphate is important for bones, teeth and muscles
- calcium is important for bones and teeth, helps blood to clot and also helps the muscles, including the heart muscle, to work.
Further tests
Your child may need further tests to confirm that he or she has proteinuria, what is causing it, and whether he or she has another health condition. These tests will help decide whether your child needs any treatment.
Imaging test
Some children need imaging tests. These use special scanners that get images (pictures) of the inside of their body.
An ultrasound scan looks at the shape and size of kidneys and other parts of the urinary system. A small handheld device is moved around your child’s skin and uses sound waves to create an image on a screen.
Occasionally, other imaging tests are needed.
Kidney biopsy
Some children need a kidney biopsy. A tiny sample of a kidney is removed from the body with a needle. This is examined under a microscopes. special medicines are used so your child will not feel any pain or can sleep through the procedure. It can take a few weeks to get the results.
Referral
Your child may be referred to a paediatrician, a children’s doctor usually based in a hospital, or a paediatric nephrologist, a doctor who treats children with kidney problems. This may happen if your child has persistent proteinuria (that does not go away), or a high level of proteinuria.