In unilateral renal hypoplasia, one kidney is smaller than usual because it has not fully developed while a baby is growing in the womb. (‘Unilateral’ means one side.) The other kidney usually looks and works as normal, and may grow larger to help do the work of two kidneys.

Most people have no long-term problems with unilateral renal hypoplasia, and some do not know that they have one kidney that is smaller than usual.

Before birth

Bilateral renal hypoplasia may be suspected on the 20 week antenatal ultrasound scan, which looks at your baby growing in the womb.

The scan also measures the amount of amniotic fluid (or liquor), the fluid that your baby floats in. The baby’s kidneys start making urine and pass this out into the amniotic fluid. This fluid protects your baby from getting hurt from the outside and helps his or her lungs mature so he or she is ready to breathe after birth.

If there is not enough amniotic fluid (oligohydramnios), this may be a sign that the kidneys are not working well, and that there may be problems breathing after birth.

You may need more ultrasound scans during the pregnancy to find out how the hypoplasia is affecting your baby. It does not usually have an impact on how your baby is delivered.

Tests after birth

After your baby is born, he or she may need some imaging tests (scans) to confirm the condition and look for any complications. These use special equipment to get pictures of the inside of the body.

An ultrasound scan is usually done first. This looks at the shape and size of your baby’s 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.

  • DMSA scan –checks for any damage on the kidneys. A chemical that gives out a small amount of radiation is injected into one of your child’s blood vessels. This chemical is taken up by healthy parts of the kidney and a special camera takes pictures.
  • MAG3 scan – for babies who also have antenatal hydronephrosis, this shows how much blood is going into and of their kidneys, and whether they are passing urine normally. As in the DMSA test, a chemical that gives out a small amount of radiation is injected into a blood vessel, and a special camera takes pictures.
  • Cystourethrogram or MCUG (sometimes called a VCUG) – usually for babies and children who are suspected of having  vesicoureteral reflux (VUR). In this condition, some  urine refluxes (goes back up) the wrong way up the ureters towards, and sometimes into, the kidneys. This test can check how your baby is passing urine. A special X-ray machine takes a series of images of the bladder while your baby is passing urine.

Unilateral renal hypoplasia complications and treatment

In most cases, babies do not need treatment. A small number of children have symptoms or complications, which may not happen until later in life. These may need follow up or treatment, such as medicines.

High blood pressure

Some children develop hypertension, blood pressure that is too high.

If your child has hypertension, he or she will need to reduce their blood pressure so it is in the healthy range. Your child will probably need to eat a no-added salt diet, and may need to take medicines, to control his or her blood pressure. It is also recommended that all chidren, especially those with hypertension, keep to a healthy body weight and exercise regularly.

Occasionally, children who have a hypoplastic kidney that is not working well and have blood pressure that cannot be controlled will need the hypoplastic kidney removed in an operation called a nephrectomy. You may be referred to a paediatric nephrologist, a surgeon who treats children with problems in their urinary system, to discuss the operation.

Urinary tract infections

Some children get urinary tract infections (UTIs), when germs get into the urine and travel up the urinary tract (or system) and cause an infection, usually in the bladder. Babies and children with UTIs may become irritable, have a fever, have pain on weeing, feel sick or be sick.

UTIs that keep coming back are more in children who also have vesicoureteral reflux (VUR), when some urine refluxes (goes back up) towards, and sometimes into, the kidneys.

If your child has a UTI, he or she will need to take antibiotics, medicines that kill the germs.

If you think your child has a UTI, seek medical advice.

Chronic kidney disease

In many people with unilateral renal dysplasia, the other kidney works normally. The normal kidney can work harder to compensate and do the work of two kidneys.

Sometimes children with unilateral renal dysplasia have an abnormality in the other kidney. If the other kidney does not work normally, your child may have reduced kidney function. He or she may be at greater risk of progressing to later stages of chronic kidney disease (CKD), and will need more monitoring.

About the future

Many people live normal lives with unilateral renal hypoplasia. The other kidney usually works normally, and may grow larger to help do the work of two kidneys.

Your child should be able to do all the things other children their age do. He or she can go to nursery and school, play with other children and stay active.

Follow up

In the first few years of his or her life, your child may need to go back to the hospital for some tests. Later, he or she will need to see your family doctor about once a year. It is important to go to these appointments, even if your child seems well. You will also have the opportunity to ask any questions. At these appointments your child will have:

  • his or her blood pressure measured, to check for hypertension
  • urine tests – to check for for protein in his or her urine (proteinuria), which may be a sign of problems in the kidney. You or a nurse will collect some of your child’s urine in a small, clean container. A dipstick is dipped into the urine – this is a strip with chemical pads that change colour if there is protein .

Living healthily

Your child can help protect his or her kidneys, and reduce the risk of hypertension later in life, by leading a healthy lifestyle through their child and adult years. This includes:

  • eating a healthy diet – with at least five servings of fruit and vegetables a day, taking care not to eat too much salt, sugar and fats (especially saturated fats)
  • getting plenty of exercise
  • not smoking.

Further support

This can be a difficult and stressful experience for you and your family.

If you have any concerns or need additional support, speak with your doctor or nurse.

More information

  • Ultrasound scan

    Uses sound waves to look at the inside of the body, such as the kidneys and other parts of the urinary system.

  • Blood pressure

    Blood pressure (BP) is the force, or pressure, that makes the blood flow round the body. It is very important that your child’s blood pressure is in a healthy range. If it is too high or too low, your doctor will try to find out what is causing this.

  • Urine tests

    Your child may have urine tests at the clinic or hospital to help diagnose a condition or find out how well a treatment is working.