What You Need To Know About Multicystic Dysplastic Kidney

If you’re pregnant, you may be delighted and excited to welcome your baby into your family. However, the news that your baby could have a multicystic dysplastic kidney can come as a shock. 

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What is a multicystic dysplastic kidney?

Multicystic dysplastic kidney (MCDK) is a condition that results in abnormal development of the kidney before birth. The condition can affect one kidney (unilateral) or both kidneys (bilateral). 

MCDK happens when the kidneys fail to grow into their proper shape and instead develop fluid-filled cysts. The cysts can be of varying sizes and look like a bunch of grapes. 

A multicystic dysplastic kidney doesn’t function. When the condition affects one kidney, the other usually grows to compensate for the functioning of the one with the cyst.

The kidney begins to develop 4-6 weeks after conception through a series of complex stages. When something goes wrong at any stage, it will result in bundles of cysts and abnormal tissues.

The role of the kidneys is to filter waste products and regulate the body’s water and salts. Kidneys also control blood pressure and the production of red blood cells.

When both kidneys are affected, the baby will be stillborn¹. This is because the kidneys can no longer produce fetal urine that composes amniotic fluid, essential to support pregnancy to full term and for the lungs to grow. 

In the rare cases that a baby is born with bilateral MCDK, they will have no working kidneys. In this case, the baby will pass away after birth².

What causes kidney dysplasia?

MCDK occurs during fetal development, but its exact cause is unknown. In most cases, the condition occurs randomly, so it's not caused by anything the mother did or didn’t do before or during pregnancy. 

Experts suspect kidney dysplasia might be due to early blockage of the urine flow as it leaves the kidney. Studies³ show that MCDK rarely occurs because of genetics. If your doctor suspects genetic mutations to be the cause, they will conduct genetic testing, followed by genetic counseling. Counseling helps the mother cope and understand more about the condition.

Studies⁴ also show that MCDK is associated with exposure to viral infections before birth. The common environmental risk factors⁵ are air pollution, phthalates, and metal exposure, but there are no reports on how much each contributes to kidney problems.

How common is multicystic dysplastic kidney?

MCDK is the most common fetal abnormality⁶ and the second most common cystic renal disease, after polycystic kidney disease.

One in every 4,300 live births⁴ has a unilateral multicystic dysplastic kidney, affecting males more than females. 

Many cases are detected during fetal ultrasound checks as early as 15 weeks. When detected early, doctors can choose the proper treatment and management plan. Unlike unilateral MCDK, bilateral MCDK is rare. If detected early, your baby will need routine treatment and monitoring.

Multicystic dysplastic kidney diagnosis

MCDK needs a radiologic evaluation for a diagnosis. A radiographer will conduct a postnatal ultrasound along with the following:

Renal ultrasound (RUS)

A RUS, also known as renal ultrasonography⁷, is a procedure that examines one or both kidneys. The non-invasive test uses a transducer which the technician passes over the fetus. This produces sound waves that bounce off the kidney, transmitting images to a computer.

The black and white images produced by the ultrasound show the kidney's internal structure. They display any abnormal tissues and cysts for diagnostic purposes.

Voiding cystourethrogram (VCUG)

VCUG takes images of the urinary system. During the test, a radiologist will insert a catheter in your baby's urethra (a tube that drains urine from the bladder) and then fill it with contrast material. This liquid allows the technician to see how your baby’s system is working.

Your radiologist will use a technique known as fluoroscopy as the contrast material fills the urethra and again when the baby empties its bladder. Onscreen X-ray videos will show how the liquid flows through the urinary system. 

In a healthy body, urine flows from the kidney through the ureter to the bladder. In case of abnormalities, the liquid will not flow, signifying a blockage on the urine path. The test can also show whether the baby's urine is moving in the wrong direction. This happens if there’s a problem with the kidney, causing the urine to flow back into the kidney. 

Intravenous pyelogram (IVP)

An intravenous pyelogram (IVP) is an imaging test that observes the kidneys and the ureter. During the test, a radiologist injects a contrast dye into your baby's veins and uses x-ray images to monitor how the dye flows from the kidney to the ureter and bladder.

If the dye flows slowly or fails to flow, it may indicate that the baby has a kidney blockage. The results could also mean that the kidney, ureter, or bladder is not working as it should, prompting further investigation.

Treatment for multicystic dysplastic kidney

While there's currently no cure for a dysplastic kidney, your baby’s medical team can manage the condition. The treatment will depend on the severity of the condition.

If your child has mild MCDK, one kidney is fully functioning. In such cases, there's no need for treatment as your child can live a healthy life with one kidney. The healthy kidney will take over and compensate for the dysfunctional one.

If your child has unilateral MCDK, they will likely develop the following complications:

  • Urinary tract infections (UTIs)

  • Renal scar formation

  • High blood pressure⁸

A severe case of dysplastic kidney means the kidneys are not functioning well. A kidney with significantly decreased functioning will require treatment for related complications, such as: 

  • Bone disease

  • High blood pressure

  • Anemia

  • Excess protein in the urine⁹ (proteinuria)

Treatments for dysplastic kidney include:


MCDK has no cure. Treatment often involves regular monitoring through ultrasound examinations. Pediatric urologists who recommend kidney monitoring will perform ultrasound examinations until the baby's kidney regresses and eventually disappears.

Research shows that imaging is the best way to manage the condition. Imaging results can identify the affected kidney and track its progress after birth. If the kidney shows no sign of disappearing, your child’s urologist will recommend surgery to remove it.


Surgery removes the need for long-term monitoring since there won't be hypertension or tumor risks. A surgeon will conduct a laparoscopic nephrectomy (kidney removal) through a small skin incision to the front or back:

  • Front (transperitoneal): This option allows the surgeon to remove the ureter as well

  • Back (retroperitoneal): This method allows for quick recovery

If your baby has two nonfunctional kidneys and survives pregnancy, it will need a transplant or dialysis. 

Multicystic dysplastic kidney complications

In many cases, a dysplastic kidney is not a cause for alarm, especially when one kidney is healthy and fully functioning. However, you should have your child evaluated after birth to check for abnormalities associated with dysplastic kidneys, such as:

Vesicoureteral reflux

Vesicoureteral reflux (VUR)¹⁰ is an abnormal urine flow from the bladder to the ureter and kidneys. Doctors class VUR from grade I to V, with grade I being mild and V most severe.

Ureterovesical junction obstruction

Ureterovesical junction obstruction is a blockage in the junction where the ureter meets the bladder. The blockage prevents urine from flowing correctly or causes urine to back up into the urinary system.

Ureteropelvic junction obstruction

Ureteropelvic junction obstruction is a blockage where the renal pelvis connects to the ureters. This blockage results in decreased urine flow and increased pressure in the kidney.

All these conditions can damage the kidneys, but surgery can correct them. In other cases, they may resolve on their own. Your doctor will select the best course of action depending on the radiologic test results and a pediatric urologist's recommendations.

When to visit a doctor

Multicystic dysplastic kidney doesn't have any signs or symptoms. The condition is detected during a routine antenatal ultrasound or when your doctor sees a mass on a routine physical checkup. Your doctor will refer you to a fetal center for more evaluation if they suspect MCDK. 

The lowdown

The news that your baby has multicystic dysplastic kidney can be disheartening. You may feel confused or worry that it is your fault, but MCDK occurs randomly. 

If your child has unilateral MCDK, they can live with one fully functioning kidney. They may have a few health problems, but your doctor can discuss treatment options with you. For bilateral MCDK, your doctor will recommend kidney dialysis or transplant.

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