Stage 1 CKD is diagnosed (identified) when a child has a chronic kidney condition or anomaly (that lasts a long time). If your child has certain symptoms or signs, or if your baby had problems before birth, during pregnancy, your doctor will speak with you about the symptoms, examine your child and arrange some tests. 

Your child will need to return to the clinic or hospital for follow-up appointments. It is important to go to these even if your child feels well.

Glomerular filtration rate and stages

Your doctor can measure your child’s kidney function (how well his or her kidneys are working) by measuring the glomerular filtration rate (GFR). This helps to work out the stage of CKD.

Inside the kidneys are many tiny filters called glomeruli, which help clean blood. The GFR is the volume of blood that filters through the glomeruli. If the GFR is lower than normal, less blood is passing through the glomeruli. The kidneys are not working as well as normal. 


The GFR measures the volume in millilitres (mL) that the kidneys filter each minute (min). This is adjusted for your child against a standard adult body size, which has a surface area of 1.73  metres squared (m2). 

  • The GFR for kidneys that are working at 100% (healthy kidneys) is 90 mL/min/1.73m2 or higher. 
  • The GFR for kidneys that are working at 50% (half as well as healthy kidneys) is 45 mL/min/1.73m2.  

More about the stages of CKD with the GFR.

How GFR is measured

The GFR is measured by finding out how quickly the kidneys remove a substance from the blood into urine. There are two main methods of measuring GFR in children. Both of these use needles – a special gel or cream can be used to help your child stop feeling any pain.

  • Blood test – this finds out the estimated glomerular filtration rate (eGFR). A small amount of blood is taken from a vein, with a needle and syringe. The amount of a waste product called creatinine is measured and used to calculate the eGFR. This is not an accurate measurement, but it is very close and is good enough for many children.
  • Radioactive tracer – this is a more accurate measurement of the GFR, and is needed in some children. A small amount of a chemical that gives out radiation (a form of energy) is injected into a vein in your child’s arm. Several blood samples are taken over a period of time. This finds out how quickly your child’s kidneys filter the chemical out of the blood. 

More about these tests to measure GFR in Blood tests

Blood tests

Other blood tests may be used to check for other substances in the blood. These include:

  • electrolytes – important chemicals in the body that are also found in foods
  • urea and creatinine – waste products made by the body
  • full blood count – to count the number of types of blood cells, and iron and some vitamins, to check for a problem in the blood called anaemia
  • protein levels 
  • parathyroid hormone (PTH) and other hormones – to check for problems with bone development and growth
  • sugars 
  • fats (including cholesterol)

Read more about blood tests in CKD


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.

Urea and creatinine

The body makes some chemicals after it uses energy. Urea is made from the protein we eat, and creatinine comes from our muscles. These are waste products (not needed by the body). The kidneys remove them from the body into urine.

If the kidneys are not working as well as they should, there may be a higher amount of urea or creatinine.


A full blood count (FBC) – counts the numbers of types of blood cells, the living parts of blood. Children with late stage CKD may develop anaemia. This means that the blood has fewer red blood cells or less haemoglobin, a substance that is in red blood cells. Because red blood cells and haemoglobin carry oxygen around the body, children often feel weak and tired, and may look paler than usual.

The level of iron and some vitamins are also measured – these help to prevent anaemia. If these are low, your child may be given supplements. 

Protein in the blood

Some children with CKD have more protein than usual in their urine (proteinuria). This happens when the kidneys leak protein. In some cases, enough protein is lost in the urine to cause a drop in the levels of protein in the blood. 

Albumin is one type of protein. Because it is small, albumin is more likely to be leaked.

Hormones for bone development and growth 

A hormone called parathyroid hormone (PTH) is released into the blood stream by the parathyroid glands, which are in the neck. Both PTH and vitamin D work with minerals such as calcium and phosphate for bone development. In later stages of CKD, some children have too much PTH. If this happens, your child may need medicines to keep PTH at the right level.

Other hormones called growth factors help the body grow. In CKD, the levels of growth factors may be normal, but may not be producing normal growth. Some children with more severe CKD may need extra growth hormone.

Urine Test

Urine tests may also be used, especially to check for protein or blood in the urine (wee), which are signs of kidney disease. You, or a nurse, will need to collect some of your child’s urine in a small, clean container. 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. The sample may also be sent to a laboratory for more accurate tests.

Imaging tests

Some children need imaging tests (scans). These use special equipment to get images (pictures) of the inside of their body.

Types of imaging tests

  • Ultrasound scan: A small handheld device is moved around your child’s skin and uses sound waves to create an image on a screen. 
  • DMSA scan: a chemical that gives out a small amount of radiation (energy) is injected into one or your child’s blood vessels. This chemical is taken up by healthy parts of the kidney and a special camera takes pictures. These show how well the kidneys are working and whether there are any scars.
  • MAG3 scan: like the DMA scan, a chemical that gives out a small amount of radiation is injected into one or your child’s blood vessels veins and travels into his or her kidneys. A special camera takes pictures, which show how much blood is going into and out of his or her kidneys and looks at how well the kidneys are draining urine.
  • MCUG (or VCUG): a thin tube is placed in your child’s urethra and a dye is put through to reach his or her bladder. An X-ray machine takes a series of images of your child’s bladder while he or she is passing urine. This can see whether and how far the urine refluxes (goes back up the wrong way up the ureters, towards, and sometimes into, the kidneys.
  • CT scan: your child lies on a bed that moves into a large tunnel. This takes a series of X-ray images at different angles. This builds up a detailed picture of their kidneys.

Kidney biopsy

Your doctor may recommend a kidney biopsy. A tiny piece of one kidney is removed from the body with a needle, and examined under microscopes. Special medicines are used so your child does not feel any pain or can sleep through the procedure. 

A kidney biopsy can give more information about how much damage there is in your child’s kidney. It can take a few weeks to get the results.