When the kidneys are developing within the womb tubes (called ureters) grow up from the bladder region and join with the developing kidney. What usually happens with MCDK kidney is that the ureter on one side never reaches the kidney area. As a result, the kidney becomes abnormally developed (dysplastic) with a number of cysts within the kidneys (hence multicystic). We tend to put the terms together to call it multicystic dysplastic kidney or MCDK.
The MCDK problem usually occurs only on one side. Your child can lead a perfectly normal life as long as the other ‘normal’ kidney is ok.
Note that MULTICYSTIC DYSPLASTIC is NOT the same as POLYCYSTIC KIDNEYS which refers to an inherited disease affecting both kidneys.
Most MCDK kidneys are recognised as a collection of cysts within the kidney that may be abnormally large at some time during pregnancy. It is unlikely that the cysts will be confused for a kidney that has a blockage (hydronephrosis) or any other kidney problem.
Since one kidney is normal there should not be any lack of womb fluid or interference with baby’s development within the womb. There is no need to deliver babies early and even if the MCDK kidney is large this should cause no problems at delivery.
As long as baby is well and passing urine normally then discharge home should not be delayed. Sometimes the MCDK kidney can be felt after birth but it is very unlikely that the kidney will be so large that removing it has to be considered.
The tests that are done are to prove that the MCDK kidney is not functioning and also to rule out any other problems such as vesicouretic reflux (passage of urine back from the bladder to the kidneys) which can occur in both the MCDK kidney and the normal kidney.
The tests will be explained to you in the clinic. You may also meet the nurse who will coordinate the tests in case you have any questions.
You will see the consultant back in the clinic who will review all the tests with you. If they confirm that the MCDK kidney is non-functioning then they will arrange to follow the baby in the clinic at certain intervals. Usually this will be at 6 and 12 months of age and then yearly until 5 years and then every couple of years until 10 years of age.
Follow up studies to date on children with MCDK kidneys show that there is at least a 60% chance that the MCDK kidney will disappear or reduce in size in the first 2 years of life. This is why a further ultrasound is done at 2 years. Even if the MCDK kidney is still visible at 2 years there is still a good chance that the kidney will disappear by 5 years. It is very rare for the MCDK kidney to enlarge in size and most of them will disappear in time.
A single kidney is the commonest abnormality found in the general population and it is likely that many people had an MCDK kidney which disappeared with time to give them a single kidney in adult life.
If your child was found to have vesicoureteric reflux then antibiotics are usually given once at night for the first 2 years. This does not entirely remove the risk of infection but makes it more unlikely. The bladder x-ray is not usually repeated at any time unless the baby has recurrent infections.
Since most of these kidneys disappear with time, then an operation is not justified. There are rare reports of blood pressure (hypertension) being due to MCDK. Even rarer are reports of kidney tumours (cancer) developing in all types of abnormal kidneys. However, current evidence suggests the risk with an ordinary MCDK kidney is minute.
Several centres are gathering knowledge about MCDK kidneys as it is only in the last 10 years or so that such kidneys have been detected on antenatal ultrasound. Speak to your consultant about further information if you require more details.
Sukthankar S, Watson AR. Unilateral multicystic dysplastic kidney disease: defining the natural history. Acta Paediatrica 2000;89:811-813.
NKF Controlled Document No. 17, Multicystic Dysplastic Kidney (MCDK) Explained, written 17 February 2004. Last reviewed 1 June 2007.
Content compiled by A R Watson and members of the Children and Young People’s Kidney Unit, City Hospital, Nottingham NG5 1PB.
The National Kidney Federation cannot accept responsibility for information provided. The above is for guidance only. Patients are advised to seek further information from their own doctor.
Page created: 13 June 2007
Last updated: 13 June 2007
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