What is MCDK?
Multicystic dysplastic kidney is a kidney that did not develop properly in the womb. Instead of normal kidney tissue, many cysts of different sizes form, not connected to one another. Such a kidney does not make urine, that is, it does not work.
It occurs in about 1 in every 3000–4000 births and is usually on one side. It is often found on fetal ultrasound in the second half of pregnancy.
MCDK is not the same as inherited polycystic kidney disease. In polycystic disease both kidneys are affected and the course is different.
How is it different from hydronephrosis?
On ultrasound, MCDK sometimes looks like severe hydronephrosis. The difference is that in hydronephrosis the cyst-like spaces (calyces) connect to a central renal pelvis and there is kidney tissue. In MCDK, the cysts are not connected to each other and there is no central pelvis. In uncertain cases, a DMSA scan confirms that the kidney does not work.
Course
The cystic kidney often shrinks as the child grows. In about half of children it becomes almost invisible on ultrasound by age 5. The healthy kidney, meanwhile, usually grows a little larger than normal and does the work on its own.
Treatment and follow-up
Most children need no surgery at all. The main task is to protect the healthy kidney:
- ultrasound in the first year and periodically afterward: the growth of the healthy kidney and the shrinking of the cystic kidney are followed,
- if the other kidney is dilated, further tests to rule out reflux or narrowing,
- as the child grows, periodic blood pressure checks and urine tests (protein),
- a urine test if there is a fever.
Removal of the cystic kidney is discussed only if the kidney grows very large and interferes with breathing or feeding, or if pain, infection or high blood pressure develops. In such cases the operation is usually done laparoscopically.
Note for pediatricians and family doctors
In children with MCDK, an anomaly of the contralateral kidney (reflux, UPJ obstruction) is found in about one in four, so the contralateral kidney should be carefully assessed with ultrasound. During long-term follow-up, blood pressure and urine protein should be checked periodically.
What happens at the visit?
- Ultrasound assesses the cystic kidney and, most importantly, the size and structure of the other kidney.
- If the diagnosis is uncertain, a DMSA scan or MAG3/DTPA confirms that the cystic kidney does not work.
- A follow-up schedule and advice on living with a solitary kidney are provided.
Frequently asked questions
Can a child live normally with one kidney?
Yes. The healthy kidney usually grows and does the work of two kidneys. The child grows normally and can play sports. Blood pressure and a urine test simply need to be checked periodically.
Doesn't the cystic kidney need to be removed?
In most cases, no. The kidney usually shrinks on its own. Removal is considered only if the kidney is very large and causes compression, or if there is pain, infection or high blood pressure.
Related topics
- HydronephrosisWater on the kidney, dilated renal pelvisCondition
- UPJ obstructionNarrowing between the renal pelvis and the ureter, UPJ obstructionCondition
- Vesicoureteral refluxUreteral reflux, VURCondition
- Kidney and bladder ultrasoundUltrasound scan, sonographyTest
- DMSA scanStatic renal scintigraphyTest
Sources
- EAU Guidelines on Paediatric Urology, 2025.
- Scala C et al. Multicystic dysplastic kidney: prenatal diagnosis and postnatal outcome. Ultrasound Obstet Gynecol, 2017.
This page is for education. Decisions about your child’s treatment are made together with the doctor after an examination.