In unilateral multicystic dysplastic kidney (MCDK), one kidney does not develop properly while a baby is growing in the womb. Instead of a working kidney, there is a bundle of many cysts, which are like sacs filled with liquid.

MCDK: tests and diagnosis in pregnancy 

The 20 week antenatal ultrasound scan looks at your baby growing in the womb. Unilateral MCDK may be suspected if one of the kidneys looks different from usual.

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.

MCDK: tests after birth

After your baby is born, he or she will need some tests to confirm the diagnosis. These tests will also check whether the other kidney is normal or needs treatment.

Blood tests

Your baby may need one or more blood tests. These measure the kidney function (how well his or her kidneys are working).

Imaging tests

Your baby may need imaging tests (scans) to confirm the condition and look for any complications. These use special equipment to get images (pictures) of the inside of his or her body.

  • Ultrasound scan – 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 kidney(s). 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.

Occasionally other imaging tests are needed.

  • MAG3 scan – for babies who also have antenatal hydronephrosis, this shows how much blood is going into and out 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 antenatal hydronephrosis caused by 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 your baby’s bladder while he or she is passing urine.

Unilateral MCDK: 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 his or her 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 children, especially those with hypertension, keep to a healthy body weight and exercise regularly.

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 likely 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.

Operating to remove the kidney with MCDK

Normally, an operation is not required to remove the affected kidney. This is because in most children it does not cause any problems, and the affected kidney usually shrinks and disappears by the time the child is five years old.

Some children with unilateral MCDK who develop hypertension (blood pressure that is too high) continue to have a high blood pressure despite being treated with medicines, They may need an operation to remove the affected kidney as this can reduce the blood pressure in about two out of every three children.

In the past, children had operations to remove the kidney with MCDK because of concerns that cancer may develop in this kidney. More recent research, however, has shown that the risk of developing a kidney cancer is not increased in kidneys with MCDK, so an operation is no longer recommended.

Chronic kidney disease

In most people with unilateral MCDK the other kidney works normally. The normal kidney can work harder to compensate and do the work of two kidneys.

Sometimes children with MCDK have an abnormality in the other kidney. These may include renal hypoplasia or renal dysplasia. Part or all of the kidney does not develop properly and is smaller than usual. The kidney can usually clean blood and make urine, but may not work as well as a kidney with no abnormality.

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

Most people live normal lives with just one working kidney. The other kidney usually works normally, and may grow larger to help do the work of two kidneys. The kidney with MCDK may shrink and even disappear by the time a child becomes an adult.

Your child should be able to do all the things that 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 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 will be dipped into the urine – this is a strip with chemical pads that change colour if there is protein in the urine
  • blood tests – to measure his or her kidney function
  • his or her height and weight checked in childhood, to measure how much he or she is growing
  • ultrasound scans – to look at the kidney with MCDK to see whether it has shrunk or disappeared.

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

  • Tests and diagnosis

    Find out more detail about some of the tests used to diagnose or investigate kidney conditions.

  • Urinary tract infection (UTI)

    Urinary tract infections happen when germs get into the urine (wee) and travel into the urinary tract.

  • Chronic kidney disease (CKD)

    A life-long condition in which the kidneys stop working as well as they should over time. A team of healthcare professionals will support your child.