An Overview of Multicystic Dysplastic Kidney

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Multicystic dysplastic kidney is a result of abnormal fetal development in which one or both of the baby's the kidneys grows irregular cysts of all different sizes. In most cases, multicystic dysplastic kidney affects only one kidney, most commonly occurring on the left side in approximately one in 3,500 births.

There are some rare cases (approximately one in 10,000 births) in which both kidneys are affected, which can be very serious as the kidneys are responsible for producing amniotic fluid in the womb, which is vital to lung development in a fetus.

Diagnosis of multicystic dysplastic kidney
Verywell / JR Bee

Symptoms and Diagnosis

Development of a multicystic dysplastic kidney begins about five to six weeks into gestation when two tubes (ureters) grow into the kidneys and branch out to form a network of tubules. The tubules collect urine during fetus formation.

In the case of a deformed kidney, the urine has nowhere to travel and builds up inside the kidney, forming cysts. These cysts eventually cause scar tissue and prevent the kidney from functioning.

There are no symptoms of a multicystic dysplastic kidney. The condition is most commonly found during an ultrasound and can then be diagnosed. Other tests including a CT scan, MRI, or nuclear scan may be needed to help distinguish between a multicystic dysplastic kidney and another type of kidney blockage, such as a tumor or other abdominal mass.

It’s important to diagnose a multicystic dysplastic kidney because about 50 percent of babies who have one will also have another kidney-related complication.

Other kidney complications can include:

  • Vesicoureteral reflux (VUR): A condition in which urine flows backward into the ureter and kidney.
  • Hydronephrosis: swelling of the baby’s kidney that is a result of a buildup of urine
  • Ureteropelvic junction (UPJ) obstruction: partial or total blockage where the kidney meets the ureter, which causes urine buildup in the kidney leading to kidney obstruction and failure (also sometimes infections)

All of these conditions can result in an increase in infection, particularly urinary tract infections. Though the chances are less likely, a multicystic dysplastic kidney can also slightly increase the risk of kidney cancer and high blood pressure.


The cause of a multicystic dysplastic kidney is unknown. In some cases, it can be genetically inherited.

Most commonly, a multicystic dysplastic kidney is caused by an unknown blockage preventing urine from traveling through the kidney.

Though extremely rare, it is possible for a child to have bilateral multicystic dysplastic kidney (meaning both kidneys have the condition), which is seen on an ultrasound scan around 20 weeks into gestation. Fetuses with bilateral MCDK usually don't survive.


Once multicystic dysplastic kidney is diagnosed during an ultrasound, tests may be performed after the baby is born by a pediatric urologist, including:

Renal Ultrasound (RUS)

This is a noninvasive test that uses sound waves to make images of the baby’s kidneys, ureters, and bladder to see what abnormalities are present.

Voiding Cystourethrogram (VCUG)

An X-ray that examines the urinary tract by inserting a catheter into the baby’s urethra (the tube responsible for draining urine out of the bladder). Through the catheter, the bladder is filled with a liquid dye and X-ray images are taken of the bladder filling and emptying. This test helps show if there is a reverse flow of urine back into the uterus and kidney (called vesicoureteral reflux).

At one point, all multicystic dysplastic kidneys were removed surgically. Nowadays,removal of the abnormal kidney is usually not necessary. Treatment of a multicystic dysplastic kidney varies depending on the severity of the abnormal kidney. In addition to these types of tests, your pediatric urologist may simply monitor the kidney for the first three to four months of life by performing frequent renal ultrasounds to see if the size of the kidney has changed.

A multicystic dysplastic kidney may grow, stay the same size, or in most cases, shrink over time and completely disappear, leaving the baby with one healthy, functioning kidney.

If the multicystic dysplastic kidney is not shrinking, a surgery called a nephrectomy is often necessary. Depending on the patient, this procedure can be done robotically. In some cases, a laparoscopy is performed, which is a minimally invasive procedure.

The child will be given general anesthesia and parents can expect their child to stay overnight in the hospital for one to two nights to be monitored. A parent or guardian will also likely be able to stay in the room to help with comfort and care.


Hearing that your baby has a multicystic dysplastic kidney diagnosis at one of your prenatal scans can be extremely unsettling. However, a baby who is diagnosed with one multicystic dysplastic kidney is likely to have a normal, healthy life with no other complications resulting from this condition. It’s completely possible to function with one kidney—a single kidney can do the work of two without adding stress to the body.

Once the multicystic dysplastic kidney is removed (or goes away), yearly monitoring and healthy habits will need to be established to ensure the remaining kidney stays healthy. Depending on the patient, excess salt and protein may need to be monitored in the diet. Regular exercise and a healthy weight are also important. Regardless of the kidneys, these are normal regulations for a healthy lifestyle.

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