Nephrotic syndrome: tests and diagnosis
Your doctor can diagnose nephrotic syndrome by doing a physical examination and asking about the symptoms. Your child will need one or more urine tests, and may need other tests, such as blood tests or imaging tests.
Urine tests
You or a nurse will collect some of your child’s urine in a small, clean container for a urine test.
A dipstick, a strip with chemical pads that can change colour, is dipped into the urine. It can test for protein. Some dipsticks can also test for other substances, such as blood and sugar.
The urine sample may also be sent to a laboratory for more testing.
Some children will need more than one urine test.
Urine tests: checking for protein
The dipstick urine test shows whether there is any protein in the urine, but does not give an accurate measurement. This can be calculated in the laboratory. The amount of protein is compared to the amount of creatinine, a waste product made in the body, which is normally removed by the kidneys into urine.
- The urine protein:creatinine ratio (PCR) compares the amounts of protein and creatinine in the urine.
- The albumin:creatinine ratio (ACR) compares the amounts of albumin, one type of protein that is most likely to be leaked in nephrotic syndrome, and creatinine in the urine.
Urine tests: checking for sodium and osmolality
Your child’s urine may be checked for the amount of sodium (salt) and how concentrated it is – this is called the osmolality. These help find out if a child is at risk of hypovolaemia (not enough blood in the blood vessels).
Blood tests
- The amount of protein in the blood, including a type called albumin, can be measured. Because albumin is small, it is more likely to leak through the glomeruli, which means there may be less albumin in the blood.
- Antibodies can be identified. These are special proteins made by the immune system to identify and kill specific germs.
- The amount of urea and creatinine can be measured. These are waste products made in the body, which are normally removed by the kidneys into urine. They may build up in a relapse of nephrotic syndrome if there is hypovolaemia (not enough blood in the blood vessels).
- The kidney function can be measured by the glomerular filtration rate (GFR). The GFR is the amount of fluid the kidneys filter each minute. It can be estimated by measuring the amount of creatinine in the blood.
- The amounts of different types of blood cells can be measured in a full blood count.
A small amount of blood will be taken from a vein with a needle and syringe for a blood test. The blood test results can give the doctor more information, including:
- the level of protein in the blood
- information about the immune system
- how well the kidneys are working – this is called the kidney function
- the number of types of blood cells.
Imaging tests
Some children need imaging tests (scans). These use special equipment to get images (pictures) of the inside of their body.
- 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.
- Chest X-ray – for children with breathing problems, this test checks for any fluid (liquid) around the lungs. Your child sits or lies still for a few seconds while a machine takes X-ray images.
Occasionally, other imaging tests are needed.
Kidney biopsy
A kidney biopsy is not usually needed, but your doctor may recommend one to find out if there is damage is in the kidney. This is especially important if your child has relapses, as some medicines that are used to treat the nephrotic syndrome may harm the kidneys.
A tiny sample of a kidney is removed from the body with a needle – special medicines are used so your child will not feel any pain or can sleep through the procedure. The sample is sent to laboratory where it is looked at under microscopes.