Skip to content
How It Works
Explore
Resources Ask a Question
Who It's For
Patients
Decode results, prep for appointments, weigh options.
Caregivers & advocates
Carry the research load for someone you love.
Providers & clinicians
Resources for patients in your practice.
Log In Ask a Question
PubMed This is a summary of 15 peer-reviewed journal articles Updated
Pediatric Nephrology · Multicystic Dysplastic Kidney

A Developmental Glitch: How MCDK Happens

At a Glance

Multicystic Dysplastic Kidney (MCDK) is a non-genetic developmental error occurring during early pregnancy where one kidney fails to form. It develops isolated, non-communicating cysts with zero function. MCDK is a sporadic, one-time event, and the other kidney typically remains perfectly healthy.

Understanding how Multicystic Dysplastic Kidney (MCDK) happens can help ease the common fear that a parent “did something wrong” or that the child has a progressive disease. MCDK is a developmental error that occurs very early in pregnancy and is generally a one-time event, rather than a condition that will spread to the other kidney [1].

The Biology: A “Misfire” in Development

During early pregnancy, a baby’s kidneys form when two different types of early tissue (the ‘tubes’ and the ‘filters’) connect and start communicating [2][3].

In a typically developing baby, this connection signals the creation of healthy kidney tissue. In MCDK, this connection is disrupted [2]. Because the tubes and filters fail to connect properly, the kidney does not form. Instead, it turns into multiple non-communicating cysts—fluid-filled sacs that are completely isolated from one another—and fibrous scar tissue [4][5]. This process is part of a broad group of developmental issues called CAKUT (Congenital Anomalies of the Kidney and Urinary Tract) [2][6].

What MCDK Is NOT: Avoiding Common Confusion

It is very common for parents to search “kidney cysts” online and find terrifying information that doesn’t apply to their child. It is critical to distinguish MCDK from two other conditions:

1. It is NOT Polycystic Kidney Disease (ADPKD)

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a genetic condition that is often passed down through families [7].

  • ADPKD usually affects both kidneys and is a progressive disease where cysts slowly replace healthy tissue over many years [7][8].
  • MCDK is typically sporadic (meaning it happens by chance) and usually affects only one kidney [9]. The other kidney is almost always perfectly healthy and stays that way [1].

2. It is NOT Severe Hydronephrosis (UPJO)

Sometimes, a severe blockage at the top of the ureter (Ureteropelvic Junction Obstruction or UPJO) can make a kidney look like it is full of cysts on an ultrasound [9].

  • In UPJO (Hydronephrosis): The “cysts” are actually parts of a single, swollen drainage system that communicate (connect) with each other and a central renal pelvis [10][11]. The kidney often still has some function.
  • In MCDK: The cysts do not communicate with each other, and there is no central renal pelvis or drainage system [4][10]. The kidney has no function.

Confirming the Diagnosis

In most cases, a high-quality ultrasound is all that is needed to diagnose MCDK [12]. Doctors look for the hallmark “bunch of grapes” appearance with no healthy tissue in between [10].

If the diagnosis is unclear—for example, if the doctor cannot tell if the cysts are communicating—they may order a MAG3 Renogram (a type of nuclear medicine scan) [13][14].

  • How it works: A tiny amount of a radioactive “tracer” is put into the blood using an intravenous (IV) line. (The IV placement is often the most stressful part for a baby, but it is necessary for the test). A special camera watches to see if the kidneys pick up and drain the tracer [13].
  • What it shows: If it is MCDK, the scan will show zero uptake or function in the affected kidney [14][6]. If it is severe hydronephrosis (UPJO), the kidney will usually show at least some function [14].

Although this scan was common in the past, many doctors now rely solely on ultrasound if the picture is completely clear [12][15].

Common questions in this guide

Is Multicystic Dysplastic Kidney (MCDK) passed down genetically?
No, MCDK is typically a sporadic, one-time developmental error that happens by chance during early pregnancy. It is very different from inherited genetic conditions like Autosomal Dominant Polycystic Kidney Disease (ADPKD).
What is the difference between MCDK and severe hydronephrosis?
In severe hydronephrosis, the cysts are actually a swollen drainage system that communicate with each other, and the kidney often still has some function. In MCDK, the fluid-filled cysts are completely isolated from one another, and the kidney has zero function.
How is Multicystic Dysplastic Kidney diagnosed?
MCDK is usually diagnosed using a high-quality ultrasound, which reveals a 'bunch of grapes' appearance with no central drainage system. If the ultrasound is unclear, a doctor may order a MAG3 renogram scan to confirm that the affected kidney has no function.
Will the cysts in my child's MCDK kidney spread to the healthy one?
No. MCDK is a localized developmental glitch that almost always affects just one kidney. It is not a progressive disease, meaning the cysts will not spread to or damage the other, healthy kidney.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.How can you tell the difference between these cysts and the ones seen in polycystic kidney disease (ADPKD)?
  2. 2.Do the cysts in my child's kidney communicate with each other, or are they isolated from one another?
  3. 3.Does my child have a central renal pelvis in the affected kidney, or is it missing?
  4. 4.If the ultrasound is unclear, would a MAG3 scan help confirm that the kidney is truly non-functional?
  5. 5.Is there any sign of obstruction in the other, healthy kidney?

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 (15)
  1. 1

    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
  2. 2

    Practical Approach to Congenital Anomalies of the Kidneys: Focus on Anomalies With Insufficient or Abnormal Nephron Development: Renal Dysplasia, Renal Hypoplasia, and Renal Tubular Dysgenesis.

    Gazeu A, Collardeau-Frachon S

    Pediatric and developmental pathology : the official journal of the Society for Pediatric Pathology and the Paediatric Pathology Society 2024; (27(5)):459-493 doi:10.1177/10935266241239241.

    PMID: 39270126
  3. 3

    Renal dysplasia development and chronic kidney disease.

    Zhang L, Yang C, Liu X, et al.

    Pediatric research 2025; (98(4)):1212-1222 doi:10.1038/s41390-025-03950-0.

    PMID: 40000855
  4. 4

    "Watch and Wait" Strategy for Multicystic Dysplastic Kidney (MCDK): Status Survey of Perceptions, Attitudes, and Treatment Selection in Chinese Pediatric Urologists and Pediatric Surgeons.

    Wang Q, Shi Z, Jiang D

    Frontiers in pediatrics 2020; (8()):423 doi:10.3389/fped.2020.00423.

    PMID: 32850538
  5. 5

    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
  6. 6

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

    Gupta K, Mandal S, Mallya V, et al.

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

    PMID: 38427756
  7. 7

    International consensus statement on the diagnosis and management of autosomal dominant polycystic kidney disease in children and young people.

    Gimpel C, Bergmann C, Bockenhauer D, et al.

    Nature reviews. Nephrology 2019; (15(11)):713-726 doi:10.1038/s41581-019-0155-2.

    PMID: 31118499
  8. 8

    The First Pediatric Case of an IFT140 Heterozygous Deletion Causing Autosomal Dominant Polycystic Kidney Disease: Case Report.

    Seeman T, Šuláková T, Bosáková A, et al.

    Case reports in nephrology and dialysis 2024; (14(1)):104-109 doi:10.1159/000539176.

    PMID: 39015124
  9. 9

    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
  10. 10

    Magnetic resonance imaging for evaluation of foetal multicystic dysplastic kidney.

    Ji H, Dong SZ

    European journal of radiology 2018; (108()):128-132 doi:10.1016/j.ejrad.2018.09.025.

    PMID: 30396644
  11. 11

    Prenatal imaging of upper urinary tract abnormalities: when is MRI useful?

    Mallin SM, Forbes-Amrhein MM, Marine MB

    Pediatric radiology 2025; doi:10.1007/s00247-025-06465-2.

    PMID: 41313372
  12. 12

    Utility of renal scintigraphy in diagnosis of multicystic dysplastic kidney.

    Hannallah A, Baker ZG, De Filippo RE, et al.

    Journal of clinical ultrasound : JCU 2022; (50(6)):854-861 doi:10.1002/jcu.23172.

    PMID: 35246854
  13. 13

    Comparative Study Between Functional MR Urography and Renal Scintigraphy to Evaluate Drainage Curves and Split Renal Function in Children With Congenital Anomalies of Kidney and Urinary Tract (CAKUT).

    Damasio MB, Bodria M, Dolores M, et al.

    Frontiers in pediatrics 2019; (7()):527 doi:10.3389/fped.2019.00527.

    PMID: 32047727
  14. 14

    Posterior Urethral Valve and Prenataly Resolved Multicystic Dysplastic Kidney.

    Aluloska N, Palchevska S, Simeonov R, et al.

    Prilozi (Makedonska akademija na naukite i umetnostite. Oddelenie za medicinski nauki) 2021; (42(1)):77-81 doi:10.2478/prilozi-2021-0006.

    PMID: 33894118
  15. 15

    Multicystic dysplastic kidney: Assessment of the need for renal scintigraphy and the safety of conservative treatment.

    Carazo-Palacios ME, Couselo-Jerez M, Serrano-Durbá A, et al.

    Actas urologicas espanolas 2017; (41(1)):62-67 doi:10.1016/j.acuro.2016.05.004.

    PMID: 27666954

This page is for informational purposes only and does not replace professional medical advice. Always consult your pediatric nephrologist or urologist regarding your child's specific kidney diagnosis and imaging results.

Get notified when new evidence is published on Renal dysplasia, unilateral.

We monitor PubMed for new peer-reviewed studies on this topic and email a short summary when something meaningful changes.