Brief Description

The kidneys help filter blood thereby removing waste products and extra fluid from to body to produce urine. The kidneys also help regulate salt balance and, when things are going well, help keep a normal blood pressure. The kidneys start to form around 7 weeks of gestational age and by 12 weeks the fetal kidneys are starting to make urine. Often during fetal development, the tubes that drain the kidneys do not form properly and problems with the flow of urine can develop. Urine is easily seen on ultrasound. Problems with urine flow are therefore often seen before the babies are born because the mothers are examined with ultrasound machines.

A multicystic dysplastic kidney (MCDK) is usually caused by a complete blockage of the ureter, the tube that drains the kidney into the bladder, before the child is born. Because of this blockage, the kidney is unable to drain urine like it is supposed to and thus the kidney does not develop correctly. It is not certain when this happens in the pregnancy. It is a spontaneous reaction that happens during development. Nothing that an expectant mother did or did not do caused this condition.

Multicystic dysplastic kidneys usually do not have much function. This does not pose much of a threat because your body can function on just one kidney. If the diagnosis is determined after your child’s birth of a multicystic dysplastic kidney, your doctor will order many radiology tests to determine function, development, and any other abnormalities of the kidneys.

Below are ultrasound pictures of multicystic kidneys. This is how your child's kidney(s) may look:

Notice the large black circles on the ultrasound pictures. These are the "cysts." They are black because they are fluid filled and fluid shows up black on ultrasounds.

On a prenatal ultrasound, it is hard to determine exact diagnosis. The multicystic dysplastic kidney looks similar kidneys that have just a partial blockage in the drainage tube. These latter kidneys may be vary dilated (hydronephrotic) but still are capable of some renal work. Occasionally it is hard to tell a multicystic dysplastic kidney from a hydronephrotic kidney before the baby is born. By knowing there is a problem before birth, it is easy to make arrangements for the baby to get the appropriate tests after delivery to make the correct diagnosis.

Radiology Tests

ULTRASOUND - This test is done to check the kidney size and to follow the growth of the kidneys. The test does not involve a catheter (tube) or needles. It also helps check for any abnormalities such as hydronephrosis (dilation of the kidney).

VCUG - 15% of all babies with MCDK will have urinary reflux. Urinary reflux occurs when the urine travels backwards from the bladder to the kidney when the baby urinates. The kidney is not harmed by this sloshing of urine backwards from the bladder unless there is a urine infection present. All urine infections start in the bladder, but the presence of urinary reflux makes it possible for the infected urine to go from the bladder to the kidney. This can harm the kidney. Urinary reflux is a birth defect that generally goes away with time, as the baby gets older. However, to make sure that urinary reflux is not present, a VCUG (voiding cystourethrogram) will be obtained in the first few weeks of life. To do this test a small flexible catheter is put through the child's urinary opening (urethra) into the bladder. Contrast (dye) is injected through the catheter into the bladder and x-ray pictures are taken. When the bladder is filled, your baby will urinate and further pictures are taken of the bladder, ureters, and kidneys to see if reflux is present. If urinary reflux is diagnosed, most babies are placed on a daily antibiotic to protect the kidneys from infections.

Mag 3 Lasix or DMSA scan: Nuclear medicine scans are done to see how well the kidneys are working. Each kidney generally contributes about 50% to the total renal function. Most multicystic dysplastic kidneys contribute 0% function leaving 100% of the kidney function to come from the other kidney. This works out fine, as you only need one kidney to be healthy. The nuclear scans confirm that the good kidney is healthy, and that is important information to have.

Management

The management for a child with a multicystic dysplastic kidney requires frequent follow up for many years. Only rarely will a MCDK need to be removed in the newborn period. Most of the emphasis in newborns is to make sure that the other kidney is healthy and working fine. We have seen high blood pressure in 3 of 85 infants with MCDK and have proven that the high blood pressure comes from the abnormal kidney. In these few cases, surgical removal of the kidney was necessary to cure the high blood pressure. Without the threat of high blood pressure, we will typically just watch your child’s kidney growth with periodic ultrasounds. Many times the multicystic dysplastic kidney will decrease in size and sometimes melt away all together. Occasionally, the MCDK increases in size with time and surgery is recommended to simply take care of the problem and minimize the need for continued appointments.

Steinhardt GF, Liapis, H., Rajen, D. H., Watson, M. A., Liapis, A., .: Reduced Renin Expression And Altered Gene Transcript Profiles In Multicystic Dysplastic Kidneys. J Urol, 168:1816-1820, 2002.

Steinhardt GF, Liapis H, Yu H, and Flath A: Increased expression of platelet-derived growth factor A and collagenous matrix proteins in congenital multicystic renal dysplasia. Nephron 76:161-170, 1997

Steinhardt GF, Vogler G, Salinas-Madrigal L, LaRegina M: Induced Renal Dysplasia in the Young Opossum. J Ped Surg 23:1127-1130, 1988.

Steinhardt GF Liapis H, and Nag M,: Effects of experimental complete ureteral obstruction on PDGF-a chain and Type I collagen expression in fetal metanephric kidneys. Peds Nephrol 8:548-554, 1994.

*Ultrasound pictures taken from: Geneva Foundation for Medical Education and Research