In bilateral multicystic dysplastic kidney (MCDK), both kidneys do not develop properly while a baby is growing in the womb. Instead of working kidneys, there are bundles of many cysts, which are like sacs filled with liquid. (‘Bilateral’ means two sides.) Babies with this condition have no working kidneys.

Sadly, these babies are unable to survive. Some die during the pregnancy or within days after they are born.

Tests and diagnosis in pregnancy

Bilateral MCDK may be suspected on the 20 week antenatal ultrasound scan, which looks at your baby growing in the womb. MCDK may be suspected if one or both of the kidneys look 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.

What happens

If bilateral MCDK is suspected, you will be referred to specialist healthcare professionals as early as possible in the pregnancy. They may include a:

  • foetal medicine specialist – a doctor who specialises in the health of unborn babies (foetuses)
  • obstetrician – a doctor who specialises in pregnancy, delivering babies and the care of women after childbirth
  • paediatrician – a doctor who treats babies, children and young people
  • paediatric nephrologist – a doctor who treats babies, children and young people with kidney problems
  • neonatologist – a doctor who specialises in newborn babies.

You may need more ultrasound scans during the pregnancy to help find out whether your baby has bilateral MCDK.

In such situations, some people decide to terminate (stop) a pregnancy. This is a very personal decision. A healthcare professional will speak with you and support whatever decision you make.

Why does this happen?

Normal kidneys remove waste products from the body, and make sure the body has the right balance of water and salts. They also control blood pressure, help keep bones and teeth strong and healthy, and control the production of red blood cells. If there are no kidneys, the body cannot do this work.

While a baby is growing in the uterus (womb), he or she floats in amniotic fluid. This protects the baby from getting hurt from the outside and helps the lungs mature so that he or she is ready to breathe after birth. The baby swallows or ‘breathes in’ the amniotic fluid, helping the lungs grow and develop

Normally, the kidneys develop and start making urine. The baby passes the urine out, adding to the amount of amniotic fluid. If the baby does not have kidneys, he or she cannot produce urine, and this leads to not enough amniotic fluid – this is called oligohydramnios. This can stop the lungs fully developing.

Will it happen in future pregnancies?

Doctors are trying to understand what causes bilateral MCDK. It is sometimes caused by a genetic mutation, which means that it may be inherited from the mother or father.

However, it is very rare for a future pregnancy to result in MCDK, or other problems with the kidneys. Speak with your doctor for more information.

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.