Multicystic Dysplastic Kidney

Multicystic dysplastic kidney is a condition in which the kidney has been essentially replaced by multiple cysts. It is the result of abnormal fetal development of the kidney. There is little or no normal function to this kidney.

• Thanks to prenatal ultrasound, most instances of multicystic dysplastic kidney are discovered prior to a child's birth.
• The incidence is approximately 1 in 4,300 live births.
• Occurrence of multicystic dysplastic kidney is about equal between males and females, and the condition is most common in Caucasians.

At Boston Children's Hospital, our extensive resources for monitoring and, if necessary, performing surgical removal of kidneys include laparoscopic surgery — a minimally invasive operating technique that reduces the size of the incision and shortens your child's recovery time.

The vast majority of multicystic kidneys occur only on one side (left side). Sometimes, it occurs on both sides, and these cases are very serious, since the kidney is responsible for producing the amniotic fluid vital to lung development.

In most cases, multicystic dysplastic kidney isn't cause for alarm — your child's properly functioning kidney can provide the required amount of amniotic fluid.

It is important to have your child evaluated by a pediatric urologist after birth since the risk that the normal kidney may have an associated abnormality is as high as 51 percent. Some conditions commonly found with multicystic dysplastic kidney include:

• Vesicoureteral reflux
• Uretero-pelvic junction obstruction
• Uretero-vesical junction obstruction

These are all surgically correctable problems, and in some cases may resolve on their own. The best course for your child will depend on the results of her radiologic studies and the recommendation of our pediatric urologist.

A multicystic dysplastic kidney is diagnosed with a radiologic evaluation. This evaluation may include a postnatal (after birth) ultrasound along with:

• Voiding cystourethrogram (VCUG): A specific X-ray that examines the urinary tract. A catheter (hollow tube) is placed in your child's urethra (tube that drains urine from her bladder to the outside of her body) and the bladder is filled with a liquid dye. X-ray images will be taken as her bladder fills and empties. The images will show if there is any reverse flow of urine into the ureters and kidneys.
• Intravenous polygram (IVP): Another special X-ray of the kidneys, ureters, and bladder helps the doctor to see the organs and shows how well the kidneys drain urine.
• Renal ultrasound (RUS): A non-invasive test in which a transducer is passed over your child's kidney produces sound waves that bounce off the kidney and transmits a picture of the organ on a video screen.

Your child's pediatric urologist determines which of the tests above are most appropriate.

In the past, the precise diagnosis was difficult to determine, so all multicystic dysplastic kidneys were removed by nephrectomy (removal of the diseased kidney). With advances in medical imaging, the correct diagnosis can now be established with near certainty. This has led some clinicians to begin recommending surveillance instead of nephrectomy.

Monitoring

There is no uniform consensus on the best form of treatment for this condition. The condition is being monitored by a national registry (National Multicystic Kidney Registry), and some of their findings include the following:

• The risk of developing a malignancy within a multicystic dysplastic kidney is low. Since 1957 there have only been nine reported cases.
• The development of hypertension (high blood pressure) is also low, with only four patients of 508 within the Registry developing hypertension.

Currently, most pediatric urologists who recommend monitoring the kidney perform serial ultrasound examinations until the kidney totally regresses or becomes undetectable by ultrasound.

Surgery

Surgical removal is an option, and many parents have elected this form of treatment. With surgery, there is no further need for routine/serial surveillance because there is no risk of hypertension or a tumor arising from the kidney.

If you choose this option, your child's kidney may be removed through a small skin incision or by a procedure called a laparoscopic nephrectomy (kidney removal). Bostonb Children's is one of the few hospitals in the world to use robotic surgery technology for nephrectomy procedures. In 2001, we were the first pediatric hospital to acquire a surgical robot, and today, our surgeons perform more pediatric robotic surgeries than any other hospital in the world.

Laparoscopic nephrectomy may be:

• Transperitoneal (performed from the front): This approach is sometimes better if your child's ureter (the tube connecting the kidney with the bladder) also needs to be removed.
• Retroperitoneal (performed from the back or side): Most kidneys can be removed using this approach, which seems to permit even more rapid recovery.

During your child's laparoscopic nephrectomy:

1. She will be put under general anesthesia.
2. Only three or four punctures are used. Her kidney is removed through one of the puncture sites, sometimes using a small bag inserted into the surgical area to allow the kidney to be pulled out.
3. She is kept overnight in the hospital and then allowed to go home.

Surgery may also be appropriate when the multicystic dysplastic kidney is very large and causes difficulty with feeding or breathing due to its size.

This is a congenitally developed lesion and not related to the adult condition known as adult polycystic kidney disease.

The long-term outlook for a child with a complete or partial nephrectomy is very good, since most people have a second, normally functioning kidney that can adequately meet the body's needs.