Health Library
Bilateral Multicystic Dysplastic Kidney (MCDK)

What is Bilateral Multicystic Dysplastic Kidney (MCDK)?

Bilateral MCDK is a condition in which both kidneys are replaced by cysts.

What Is MCDK?

MCDK happens when fluid-filled pockets (called cysts) replace the healthy kidney tissue. It can happen in one (called “unilateral”) or both (called “bilateral”) kidneys. MCDK happens in about 1 in 1,000 (0.1%) to 4,300 (0.023%) babies.

What problems can bilateral MCDK cause?

  • Kidney failure: Since there is no normal kidney tissue (only cysts), the kidneys do not work. This damage is permanent.
  • No amniotic fluid: Early in your pregnancy, the placenta makes some amniotic fluid. But later, the amniotic fluid is made up of your baby’s urine. With MCDK, the kidneys cannot make any urine.
  • Small lungs: Your baby’s lungs need amniotic fluid to grow. If there is not enough amniotic fluid, your baby can have very serious breathing problems at birth.

What Causes MCDK?

The exact cause of MCDK is often unknown. It may be due to a blockage in the flow of urine along its path out of the kidney very early in development. There are rare cases when MCDK is due to a genetic condition. However, most occur randomly and are not inherited. This means that MCDK is a result of the kidneys not forming correctly in development. Kidney formation in a fetus is very complicated. It takes several steps to create a normal kidney. If there is a problem in the steps of development, the kidney may not form correctly. This leads to MCDK.

It is not caused by something you did during pregnancy. There is nothing you could have done differently to prevent it.

How Is Bilateral MCDK Diagnosed?

MCDK is often first seen on an ultrasound of your baby. Your doctors will see that both kidneys are replaced by many cysts of varying sizes and shapes (some say that it looks like a “bunch of grapes”). MRI can be used to get a more detailed look at the entire urinary tract and other parts of the baby. An ultrasound of your baby’s heart (called an echocardiogram) is often recommended because babies with MCDK have a higher chance of having heart defects.

Your healthcare team might recommend genetic testing to look for a cause for your baby’s MCDK. Genetic testing can be done by testing the amniotic fluid during pregnancy (called an “amniocentesis”) or using a blood sample from your baby after they are born.

What Does Evaluation Look Like at Cincinnati Children’s Fetal Care Center (CCFCC)?

An evaluation for bilateral MCDK involves a 2-day evaluation. On day one, the MRI, ultrasound and fetal echo are done. In some cases, not all testing can be done on day one. It will be done on day two. On day two the patient and support person will meet with a nurse coordinator, a social worker, and a genetic counselor. In the afternoon, a team meeting will be held with several specialists present. This will include maternal fetal medicine, pediatric surgery, neonatology, nephrology and/or urology. The team will share images from the MRI and ultrasound and talk about the diagnosis. If the problem is isolated to the kidneys and there are no other multiple congenital anomalies noted, the team may talk to you about serial amnioinfusions in the pregnancy. This will develop the fetal lungs to avoid breathing problems at birth. The amnioinfusions do not help with correcting the kidney problem or the kidney function. Not all fetuses that get amnioinfusions in pregnancy are lung survivors at birth. It is unclear why some babies benefit from amnioinfusions in the pregnancy, while others do not.

Intervention Options and Eligibility

Serial amnioinfusions in the pregnancy may be offered if the patient is a candidate. In cases where multiple congenital anomalies are noted, and these are not compatible with life, no fetal interventions will be offered. If a patient may be a good candidate for serial amnioinfusions in the pregnancy, the first step would be to obtain a genetic sample. This is used to rule out any dangerous genetic conditions.

A genetic amnioinfusion amniocentesis can be done to get the genetic sample since there is no amniotic fluid in the amniotic sac. A needle is used to enter the amniotic sac. IV fluid is infused. With fetal movement, some of the fetal cells slough off into the fluid. This fluid is withdrawn from the amniotic sac and sent to the lab for genetic testing.

If genetic testing results do not show any dangerous genetic conditions, the team will talk to you about the different approaches for amnioinfusions. Options are a direct approach or placement of amnioport. Direct approach would mean a needle poke every time into the amniotic sac to put in the IV fluid. The amnioport is a device that would need to be surgically placed into the mother. It involves two cuts on the mother for placement. One cut on mom’s abdomen to place the catheter into the uterus. One cut on her rib for the port. The amnioport device could be used one to three times per week to put IV fluid into the amniotic sac. If you choose serial amnioinfusions in the pregnancy, the team may require that you relocate to Cincinnati during the pregnancy. You would also need to deliver in Cincinnati.

What Else Can Be Seen with MCDK?

Some babies with MCDK have health problems outside of the kidneys, such as heart defects. If you have low or no amniotic fluid, your baby’s lungs may be small.

What does this mean for my pregnancy?

  • There is no way to fix the MCDK during your pregnancy.
  • There may be treatments for low amniotic fluid during your pregnancy to try to help your baby’s lungs grow. Your doctors will discuss treatment options with you.
  • You will have more frequent visits and ultrasounds with your doctor.
  • Babies with bilateral MCDK have an increased risk for miscarriage and stillbirth, especially if you have no amniotic fluid.
  • Talk with your doctor about the safest way and place to deliver your baby.

How Is MCDK Treated After My Baby Is Born?

Right after your baby is born, their doctors will see how well they can breathe. They may need help with breathing, which could include support from extra oxygen to a breathing tube and ventilator. Without normal amniotic fluid the lungs are usually too underdeveloped to allow babies to survive for long after birth. If the baby can breathe, they will need help with their kidneys in the form of dialysis. If the baby has enough lung tissue to survive outside the womb, the doctors will see if they are a candidate for dialysis. Without dialysis, the toxins in the blood that would normally be filtered by the kidneys will build up in the baby’s blood. This may lead to death.

Dialysis is done with a machine that helps remove extra fluid from the baby. It helps clean the blood, like an external kidney machine. The dialysis treatment would be done until the baby was eligible for a kidney transplant. This could happen around 2 years of age. The process of dialysis on a newborn is complicated. The skill of an experienced team is needed. Your baby will be cared for by a multidisciplinary team including neonatology, nephrology, urology, dieticians, endocrine, physical therapists, palliative care and other specialists.

What Are My Care Options?

The symptoms and treatments might be difficult for your baby and your family. You can choose to focus on treatments that will keep your baby comfortable, instead of treatments to extend their life. This is called “comfort care”. If you choose comfort care or would like more information about it, our team can talk with you about how to keep your baby comfortable while you spend time with them after they are born.

After learning about the diagnosis of a bilateral MCDK and the many difficulties that it can cause for the baby, families can choose to continue or to end their pregnancy. Both are decisions made by loving parents. We can help discuss these options and we will support your decision. For those who continue the pregnancy, parents often consider what “quality of life” means to them and what treatment options would best support this.

We will also talk with you about what treatments may be an option before and after your baby are born to treat their lungs and kidneys.

Last Updated 05/2021

Who treats this.

The Cincinnati Children's Fetal Care Center specializes in treating complex and rare fetal conditions.