Multicystic dysplastic kidney disease (MCDK) causes a developing kidney to form a group of cysts. The cysts resemble a bunch of grapes and cause the kidney to be nonfunctional. This condition is the result of atypical fetal development.

In most cases, MCDK is unilateral, which means it affects just one kidney. Unilateral MCDK does not typically affect life expectancy or health, as long as the other kidney remains healthy.

Bilateral MCDK is fatal in almost all cases. Some parents who learn of the condition during pregnancy opt to terminate the pregnancy.

Read on to learn more about MCDK.

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A diagnosis of MCDK means that, instead of typical kidney tissue, cysts form in the kidneys. These cysts prevent the development of healthy kidney tissue, and they cannot communicate with one another. The kidney therefore cannot function as it should.

MCDK is a congenital disease, which means it is present from birth.

Two types of MCDK can occur:

Unilateral MCDK

In unilateral MCDK, just one kidney has cysts. The kidney does not work, but the disease is usually harmless because a person can survive with one healthy kidney. However, a person born with this condition may need ongoing monitoring.

Between 1 in 1,000 and 1 in 4,300 babies are born with unilateral MCDK.

Bilateral MCDK

In bilateral MCDK, both kidneys develop cysts and are therefore nonfunctional. This condition also affects other organs, especially the lungs. It is almost always fatal, though in rare cases a child has survived with immediate, aggressive intervention.

It is a very rare disease.

MCDK is a genetic disease.

In most cases, a child inherits a copy of a defective gene from their parent, and this causes the disease. But in some cases, the condition occurs spontaneously, which means there is no family history.

Doctors do not fully understand the genetic origin of this disease, but they do know it is present at birth. One potential cause is a mutation in the HNF1B gene, which codes for hepatocyte nuclear transcription factor 1 beta. This is a protein that binds to sections of DNA to regulate the activity of other genes.

Some other factors may also cause MCDK by triggering genetic mutations that affect the development of the kidneys.

Exposure to certain medications, such as ACE inhibitors, during pregnancy, may play a role. MCDK is also more common in pregnancies in which the birthing parent has gestational diabetes. This is a temporary form of diabetes that occurs when the body stops producing or responding to insulin as it should.

People who are pregnant or plan to become pregnant should talk with a doctor about all medications they take.

Unilateral MCDK does not usually cause symptoms. However, it does mean that one kidney does not work. Children born with this condition may have a higher risk of urinary tract infections (UTIs) and high blood pressure when they become adults.

Bilateral MCDK is typically fatal. Babies born with this condition usually have significant breathing difficulties because their lungs do not fully develop. Because their bodies cannot eliminate waste, they quickly die. These babies may also have other congenital abnormalities, such as changes in the shape of the face or limbs.

In most cases, a doctor can diagnose the condition during a pregnancy. Doctors may notice cysts in the kidneys during an ultrasound, often around 20 weeks into the pregnancy.

Thereafter, a healthcare professional will evaluate potential causes for the cysts and determine whether one or both kidneys have cysts.

After birth, doctors may use the following techniques to confirm the diagnosis:

Supportive treatment can vary depending on whether a person has unilateral or bilateral MCDK:

Unilateral MCDK

In most cases, babies with this condition do not require treatment.

However, as they grow, some may experience complications that require treatment. Hypertension, or high blood pressure, may occur, in which case a doctor may recommend:

  • altering the child’s diet to reduce salt intake
  • using medications to manage blood pressure
  • making sure they get regular physical activity
  • helping them maintain a moderate weight

These measures are designed to lower the child’s blood pressure and ensure that their blood pressure stays within the typical range.

UTIs are another complication children can develop. These can cause fever and pain when urinating. Doctors may recommend antibiotics for UTIs.

People with only one functioning kidney can have a typical life expectancy as long as they do not have other kidney diseases.

Bilateral MCDK

Babies born with bilateral MCDK typically have a number of health issues and rarely survive. This condition may cause pregnancy loss, or the baby may die shortly after birth, in most cases.

If a baby survives, they may need treatment to ensure that the lungs develop. This usually involves ventilators or extracorporeal membrane oxygenation (ECMO).

ECMO involves pumping blood out of the body to an external machine — similar to the heart-lung machine — that filters the blood and removes carbon dioxide. The machines then pumps the newly oxygen-rich blood back into the body.

In rare cases, a baby may survive with immediate support at birth, including dialysis and a kidney transplant.

Even with these measures, life expectancy may be short, and treatment does not always work. For this reason, some people choose to terminate a pregnancy when a baby has bilateral MCDK. Doctors call this termination for medical reasons (TFMR).

Polycystic kidney disease (PKD) is another form of kidney disease that is present at birth. In most cases, it develops because of a gene a child inherits. It can also occur spontaneously.

While PKD also causes cysts, it is distinct from MCDK because the cysts do not entirely replace the kidney, so a person still has some kidney function. However, the cysts can grow over time and damage the kidney, eventually leading to kidney failure.

A person who has PKD in both kidneys can survive for a time, though they may eventually need a kidney transplant. A person who has MCDK in both kidneys cannot survive.

MCDK is a genetic disorder. It is present before birth, which means there are signs and symptoms before a baby is born.

“Fetal MCDK” means that the disease is evident in a fetus before birth. A doctor may notice cysts in the kidneys during an ultrasound, often around 20 weeks into the pregnancy.

Thereafter, a healthcare professional will evaluate potential causes for the cysts and determine whether the condition affects one or both kidneys.

MCDK is a congenital disease that may either affect one or both of a baby’s kidneys.

The condition may require only monitoring if it affects one kidney. If a child develops complications, such as high blood pressure or UTIs, then they may need medication.

However, when MCDK affects both kidneys, it is usually fatal, and parents may need to decide whether to continue the pregnancy.