Multicystic Dysplastic Kidney

What is multicystic dysplastic kidney?

To understand this condition, it is helpful to understand how the urinary tract works.  In simple terms, the kidneys (we typically have two) filter the blood and remove waste products that are then taken out of the body in the urine. The cortex of the kidneys make the urine. This urine is collected in the pelvis, which empties into a tube (the ureter) and then drains into the bladder. From the bladder the urine is drained out of the body through the urethra. 

During pregnancy the placenta does most of this work for the baby. The baby's kidneys start to produce urine beginning between the fifth and ninth weeks. Before birth, the urine made by the kidneys contributes to the amount of amniotic fluid that surrounds the baby. The amniotic fluid is important for the lungs development and maturing as well as giving the baby a "cushion" and providing him or her space to move.

Twenty to thirty percent of birth defects diagnosed prenatally (before birth) have to do with the urinary tract. Unilateral (one side) multicystic dysplastic kidney (MCDK) occurs in 1 in 1,000 to 4,300 babies born. MCDK is most commonly seen in Caucasian (white) babies. MCDK is seen slightly more often in boys than girls. Cases in girls are two times more likely to have bilateral (affecting both kidneys) MCDK disease along with other birth defects. The two most common birth defects seen with MCDK that are not related to the urinary tract are esophageal atresia (a condition in which the esophagus, or food pipe,  does not connect to the stomach) and heart problems. Esophageal atresia can be fixed with surgery. Most cases of MCDK occur on one side, most often on the left side.  

Sometimes MCDK will be seen on both sides (1 in 10,000 live births) or will be seen on one side with no kidney on the other side. Both of these conditions are lethal. Lethal means that the baby cannot survive after birth because there is no treatment to fix the problem.  One of the biggest reasons that these conditions are lethal is because the urine made by the kidneys adds to the amniotic fluid. If there are no kidneys or the kidneys do not function and make amniotic fluid, the baby's lungs will not develop. The amniotic fluid is needed for the baby's lungs to grow and mature. However, as long as one kidney is working there should be an enough amniotic fluid for the lungs to grow and mature. 

Multicystic dysplasia of the kidney is the most common cause of an abdominal mass in the newborn. Other names used to describe this condition can include multicystic kidney and multicystic renal dysplasia.  The ultrasound pictures will show a large, echogenic (bright white) kidney with multiple cysts (fluid filled masses) of various sizes. The MCDK kidney has little or no function. In the past, before the more routine use of ultrasound with pregnancy, these were diagnosed on physical exam after birth. However, today about 70 percent are seen on ultrasound before the baby is born. The cause of the disorder is not known.  It is suspected that it is the result of an early blockage. In other words, the flow of urine was blocked somewhere along its pathy from the cortex of the kidney before it could exit the body. We know it is not caused by anything the mother did or did not do.  

Prenatal Diagnosis of multicystic dysplastic kidney

Seventy percent of MCDK cases are diagnosed by ultrasound before a baby is born.  When your doctor performs a routine ultrasound, he or she may suspect that there is something wrong with the kidney(s) and will likely refer you to a specialist that handles high-risk pregnancies. These doctors are called perinatologists.   The diagnosis of MCDK will be confirmed by an ultrasound that looks specifically at the kidneys. The perinatologist also will exam the rest of the baby's body for other birth defects.  About 50 percent of babies with MCDK will have another problem that is related to the kidneys. Most of these are issues with the opposite kidney and are minor, but will require follow-up after the baby is born. The more common kidney issues include hydronephrosis (swelling of the kidney's pelvis) that is the result of a backflow of urine or blockage of the ureteropelvic junction (the area that the pelvis and ureter meet). Other birth defects that are not related to the kidneys will be seen more often if both kidneys have been affected with MCDK.  A genetic test may be recommended because MCDK has been associated with some syndromes and genetic disorders. The perinatologist will discuss the risks and benefits of this test with you before doing it.

How does multicystic dysplastic kidney affect my baby?

If the baby has unilateral (one-sided) multicystic dysplastic kidney disease and a normal, working kidney on the other side, this diagnosis should have very little effect.  However, if there are other birth defects seen with this diagnosis, there may be more impact on the baby.

After the baby is born, he or she will be examined by the doctor(s) for any other issues. Close follow-up care will be planned to make sure the baby stays healthy.  Approximately every three to four months during the first year of life, a renal (kidney) ultrasound will be done to look at the kidneys. The kidney with MCDK disease may increase in size, stay the same or get smaller. Many of these kidneys will slowly shrink in size. 

Very rarely, a malignancy (cancerous growth) of the affected kidney has been seen.  Another very rare problem is hypertension (high blood pressure).

How is multicystic dysplastic kidney treated?

The plan of treatment for this condition will vary from baby to baby and from doctor to doctor. In the past, before we were able to make this diagnosis before birth, many of these kidneys were removed in the operating room simply to be able to see the abdominal mass. Today, with more advanced tests (X-ray, CT scan, MRI, ultrasound) most doctors agree that the best way to care for these babies is to watch the affected kidney very closely for size changes. The opposite kidney will also be watched closely for its ability to make urine.

A renal (kidney) ultrasound will be done at four to six weeks and again at six to nine months to look at the kidneys.  Another test that may be done is a voiding cystourethrogram. This is a special X-ray that watches the kidney as it makes urine and the filling and emptying of the bladder and whether there is backward flow of urine. Other tests also may be done. The pediatric urologist (a doctor that specializes in treating urinary tract issues) will discuss these tests with you before they are done.

If the affected kidney must be removed, this procedure is called a nephrectomy. The risks and benefits of this procedure will be discussed with you before it is done.

What about after surgery?

Surgery is not usually done soon after birth for a multicystic dysplastic kidney. The kidney is watched, and most will shrink in size. However, if it grows or is causing other problems, such as interfering with breathing or eating, or the way it looks is worrisome to the doctor and/or if there is a problem with being able to come for follow-up care, a nephrectomy may be recommended.  How the kidney is removed will depend on your doctor, the size of the kidney and whether the ureter will also need to be removed. The baby will need to be put to sleep for the surgery. The hospital stay is typically just an overnight stay with a quick recovery.

Will I be able to help care for my baby or child after surgery?

Yes. Please ask your baby or child's nurse about ways to interact with and care for him or her. You may want to bring pajamas, a stuffed animal, small toy or favorite blanket from home to help make your child feel more comfortable during their stay in the hospital. 

When can my baby/child go home?

A nephrectomy requires general anesthesia (being put to sleep) and a minimum of an overnight stay. The type of surgery, possible problems and the expected length of stay will be discussed with you before the surgery is done.

What is my baby's long-term prognosis?

A baby with unilateral MCDK with no other birth defects has a normal life expectancy. For a child with only one kidney that works, that kidney may be a little bigger than normal. He or she will need follow-up to care for the rest of his or her life to make sure the kidney remains healthy. These patients also should limit the amount of salt and protein in their diet to the recommended daily requirements for their age. These patients should not be involved in contact sports to protect their one good kidney from becoming injured.  Weight should be kept at the ideal body weight and regular exercise is recommended for all people, but especially those with one kidney. Blood pressures should be checked at least annually. 

For more information, visit www.UrologyHealth.org.