Your child’s doctor will try to diagnose (or identify) AKI quickly and find out whether your child needs any treatment. Your child may need an examination, including measurement of blood pressure, urine tests, blood tests, imaging tests and a kidney biopsy.
Examination
Your doctor will talk to you or your child about their symptoms and any medicines that they take. He or she will do an examination of your child – for example, to see whether they have oedema (swelling in the body).
Your doctor or nurse will check your child’s blood pressure to see whether it is too high (hypertension) or too low (hypotension).
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.
Your doctor or nurse will place a dipstick into the urine. The dipstick 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.
Blood tests
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:
- how well the kidneys are working – this is called the kidney function
- the amount of some important chemicals
- whether the immune system is working in a different way than usual
How blood tests can show well the kidneys are working
Urea and creatinine are chemicals that are made in the body, They are waste products and normally removed by the kidneys into urine. In AKI, 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.
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.
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.
Imaging tests
Some children need imaging tests. These use special scanners that take pictures of the inside of the body. The most common tests are the ultrasound scan, echocardiogram and chest X-ray, but occasionally other tests are used.If your child needs one or more of these tests, your doctor will talk to you about the procedures, any risks and how to help your child prepare for them.
- Ultrasound: if your doctor needs to see your child’s kidneys and other parts of their urinary system, they may have an ultrasound test, which uses sound waves. Your child will lie on their back, and a short wand with jelly on its tip will be moved around the outside of their tummy. The images will be shown on a television screen.
- Echocardiogram: if your doctor thinks your child may have problems with their heart, they may arrange an echocardiogram. This also uses sound waves to look at the blood flow through the heart.
- Chest X-ray: your child may need this test – for example, if they have breathing problems, this checks if there is any fluid around their lungs. Your child will need to stay still for a few moments while a machine takes pictures of the inside of their body.
Kidney biopsy
Some children need a kidney biopsy to find out more. A tiny piece of one kidney is removed from the body with a needle. This is examined under special microscopes in a laboratory. Special medicines are used so your child does not feel any pain or can sleep through the procedure.
The results can take a few weeks.