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PubMed This is a summary of 55 peer-reviewed journal articles Updated
Pediatrics

Understanding Your Baby's MCDK Diagnosis

At a Glance

Most babies diagnosed with unilateral Multicystic Dysplastic Kidney (MCDK) live completely normal, healthy lives without needing surgery. The healthy kidney naturally grows larger to do the work of two, while the cystic kidney usually shrinks over time.

Hearing that your baby has a kidney abnormality can be an overwhelming and frightening experience. It is natural to feel a sense of shock or worry about your child’s future. However, for most families, a diagnosis of Multicystic Dysplastic Kidney (MCDK)—specifically when it only affects one kidney—is much more manageable than it first sounds. This guide is designed to help you understand what this diagnosis means and why the outlook for your baby is typically very bright.

What is MCDK?

Multicystic Dysplastic Kidney (MCDK) is a condition where a kidney does not develop properly during pregnancy [1]. Instead of forming a functional organ that filters blood and creates urine, the kidney becomes a collection of fluid-filled sacs, called cysts, that do not connect to one another [2][3].

Because the normal kidney tissue (parenchyma) has been replaced by these cysts, the affected kidney is non-functional, meaning it does not work [1][4]. In the vast majority of cases, this only happens on one side (unilateral), while the other kidney is perfectly healthy [5].

Why Did This Happen?

It is important to know that you did nothing to cause this. MCDK is usually a sporadic event, meaning it happens by chance during the complex process of fetal development [6]. While researchers are looking into specific genetic pathways (such as the PI3K-AKT-mTOR pathway) that play a role in cyst formation, most cases are not part of a larger genetic syndrome [7][8].

Three Stabilizing Facts for Parents

When you are first processing this news, it helps to focus on these three evidence-based realities:

  1. A Normal Life is the Expectation: Children with one healthy kidney (isolated unilateral MCDK) typically live completely normal, active lives without any restrictions [9][3].
  2. Surgery is Rarely Needed: Most doctors now follow a “watch and wait” approach [10]. The cystic kidney almost never needs to be surgically removed unless it causes specific problems like high blood pressure or pain [11][12].
  3. The Healthy Kidney is a Powerhouse: The human body is designed with incredible backup systems. Your baby’s healthy kidney will naturally step up to do the work of two [13].

How the Body Adapts

Your baby’s body has two remarkable ways of adapting to MCDK:

Autoinvolution (The “Shrinking” Process)

Over time, the cysts in the affected kidney often naturally lose their fluid and begin to shrink [11]. This process is called autoinvolution [14]. In many children, the cystic kidney will eventually become so small that it can no longer be seen on an ultrasound [11]. While this doesn’t happen for every child, it is a very common and normal outcome [14].

Compensatory Hypertrophy (The “Growing” Process)

Because one kidney is doing the work usually shared by two, the healthy kidney will grow faster and larger than average [13]. This is called compensatory hypertrophy [15]. This growth is a positive sign—it shows the healthy kidney is successfully adapting to ensure your baby has excellent overall kidney function [13][16]. Most children show this healthy growth by age three [13].

Long-Term Outlook

For the vast majority of children with isolated unilateral MCDK, the long-term prognosis is excellent [5]. There is a very low risk of developing high blood pressure (hypertension) or significant kidney disease later in life, provided the healthy kidney continues its strong growth [9][17].

Your medical team will likely recommend periodic ultrasounds and blood pressure checks to monitor your baby’s progress, but for most families, MCDK becomes a minor part of their child’s medical history rather than a defining health challenge [18][9].

Guide Index

Please explore the following pages to dive deeper into what to expect and how to care for your child:

01

The Biology of MCDK: How and Why It Forms

Learn how Multicystic Dysplastic Kidney (MCDK) forms during pregnancy. Understand unilateral vs. bilateral MCDK, Potter sequence, and genetic causes.

02

Preparing for Birth and Your Baby's First Days

Learn what to expect during pregnancy and delivery after a multicystic dysplastic kidney (MCDK) diagnosis. Understand birth plans and postnatal ultrasounds.

03

The Modern Way: Monitoring Without Surgery

Learn why surgery is rarely needed for multicystic dysplastic kidney (MCDK). Discover the watch-and-wait approach, autoinvolution, and routine monitoring.

04

Long-Term Care: Protecting the Solitary Functioning Kidney

Learn how to protect your child's solitary functioning kidney after an MCDK diagnosis. Find guidelines on monitoring, sports safety, medications, and UTIs.

Common questions in this guide

What is a Multicystic Dysplastic Kidney (MCDK)?
MCDK is a condition where a baby's kidney forms fluid-filled cysts instead of normal, functioning tissue during pregnancy. In the vast majority of cases, this affects only one kidney while the other remains completely healthy.
Did I do something during pregnancy to cause MCDK?
No, you did nothing to cause this condition. MCDK is usually a sporadic event that happens by chance during early fetal development, and most cases are not linked to a larger genetic syndrome.
Can a child live a normal life with only one working kidney?
Yes, children with one healthy kidney typically live completely normal, active lives with no restrictions. The healthy kidney naturally grows larger and safely takes over the filtering work for the entire body.
Will my baby with MCDK need surgery?
Surgery is rarely needed for MCDK. Most doctors recommend a 'watch and wait' approach, and the cystic kidney typically only requires surgical removal if it causes specific problems like pain or high blood pressure.
What happens to the cystic kidney over time?
In a normal process called autoinvolution, the fluid-filled cysts in the affected kidney often naturally shrink over time. For many children, the non-functioning kidney becomes so small it can no longer be seen on an ultrasound.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Does my baby have 'isolated' unilateral MCDK, or were there other findings on the ultrasound?
  2. 2.What is the current size of the healthy kidney, and does it show signs of compensatory hypertrophy?
  3. 3.Based on the ultrasound, are there any signs of vesicoureteral reflux (VUR) or other issues in the healthy kidney?
  4. 4.What is our long-term monitoring plan for blood pressure and kidney function?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (18)
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    Single-Center Experience of Pediatric Cystic Kidney Disease and Literature Review.

    Grlić S, Gregurović V, Martinić M, et al.

    Children (Basel, Switzerland) 2024; (11(4)) doi:10.3390/children11040392.

    PMID: 38671609
  2. 2

    Renal cystic diseases during the perinatal and neonatal period.

    Raina R, DeCoy M, Chakraborty R, et al.

    Journal of neonatal-perinatal medicine 2021; (14(2)):163-176 doi:10.3233/NPM-200520.

    PMID: 32986687
  3. 3

    Outcome of Multi-Cystic Dysplastic Kidneys in Children.

    Mashat SD, El-Desoky SM, Abdulaziz Kari J

    Iranian journal of pediatrics 2015; (25(5)):e2991 doi:10.5812/ijp.2991.

    PMID: 26495094
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    Troubleshooting Tips for Diagnosing Complex Fetal Genitourinary Malformations.

    Griffith AM, Woodward PJ, Kennedy AM

    Radiographics : a review publication of the Radiological Society of North America, Inc 2024; (44(1)):e230084 doi:10.1148/rg.230084.

    PMID: 38127660
  5. 5

    Prenatal diagnosis to postnatal outcomes in multicystic dysplastic kidney: experience of a tertiary center in the Black Sea region.

    Ünver G, Serin S, Tosun M, et al.

    Revista da Associacao Medica Brasileira (1992) 2025; (71(12)):e20251175 doi:10.1590/1806-9282.20251175.

    PMID: 41417372
  6. 6

    Sequence variants in the renin-angiotensin system genes are associated with isolated multicystic dysplastic kidney in children.

    Song R, Yosypiv IV

    Pediatric research 2021; (90(1)):205-211 doi:10.1038/s41390-020-01255-y.

    PMID: 33173183
  7. 7

    High Activation of the AKT Pathway in Human Multicystic Renal Dysplasia.

    Apostolou A, Poreau B, Delrieu L, et al.

    Pathobiology : journal of immunopathology, molecular and cellular biology 2020; (87(5)):302-310 doi:10.1159/000509152.

    PMID: 32927453
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    Classifying and evaluating fetuses with multicystic dysplastic kidney in etiologic studies.

    Cai M, Guo C, Wang X, et al.

    Experimental biology and medicine (Maywood, N.J.) 2023; (248(10)):858-865 doi:10.1177/15353702231164933.

    PMID: 37208928
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    Clinical outcome of children with prenatally diagnosed isolated unilateral multicystic dysplastic kidney.

    Huettinger M, Bogner G, Fischer T, et al.

    European journal of obstetrics, gynecology, and reproductive biology 2025; (312()):114112 doi:10.1016/j.ejogrb.2025.114112.

    PMID: 40517513
  10. 10

    The Outcome of Multicystic Dysplastic Kidney Disease Patients at King Abdulaziz Medical City in Riyadh.

    Alamir A, Al Rasheed SA, Al Qahtani AT, et al.

    Cureus 2023; (15(4)):e37994 doi:10.7759/cureus.37994.

    PMID: 37223165
  11. 11

    Multicystic renal dysplasia, a histomorphological spectrum: Seven years experience from a tertiary care hospital.

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    Indian journal of pathology & microbiology 2024; (67(2)):385-389 doi:10.4103/ijpm.ijpm_202_23.

    PMID: 38427756
  12. 12

    Correlation between hypertrophy and risk of hypertension in congenital solitary functioning kidney.

    Zambaiti E, Sergio M, Baldanza F, et al.

    Pediatric surgery international 2019; (35(1)):167-174 doi:10.1007/s00383-018-4389-z.

    PMID: 30374633
  13. 13

    Natural History of Contralateral Hypertrophy in Patients with Multicystic Dysplastic Kidneys.

    Gaither TW, Patel A, Patel C, et al.

    The Journal of urology 2018; (199(1)):280-286 doi:10.1016/j.juro.2017.06.075.

    PMID: 28645868
  14. 14

    Multicystic dysplastic kidney - treat each case on its merits.

    Faruque A, Narayanan S, Marley I, et al.

    Journal of pediatric surgery 2020; (55(11)):2497-2503 doi:10.1016/j.jpedsurg.2019.12.008.

    PMID: 31987520
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    The Incidence and Durability of Compensatory Hypertrophy in Pediatric Patients with Solitary Kidneys.

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    Urology 2019; (129()):188-193 doi:10.1016/j.urology.2019.04.003.

    PMID: 30986483
  16. 16

    GFR measurements and ultrasound findings in 154 children with a congenital solitary functioning kidney.

    Jørgensen CS, Carstensen R, Awneh H, et al.

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    Renal function in children with a congenital solitary functioning kidney: A systematic review.

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    Conservative Management of Segmental Multicystic Dysplastic Kidney in Children.

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This page provides general educational information about Multicystic Dysplastic Kidney (MCDK). It is not a substitute for professional medical advice, diagnosis, or treatment from your pediatric specialist.

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