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PubMed This is a summary of 14 peer-reviewed journal articles Updated
Pediatric Nephrology · Multicystic Dysplastic Kidney

The Healthy Kidney: Growth and Protection

At a Glance

In children with unilateral Multicystic Dysplastic Kidney (MCDK), the single healthy kidney naturally grows larger to do the work of two. Long-term health involves monitoring this growth, checking blood pressure, and treating urinary tract infections quickly to protect kidney function.

While the diagnosis of Multicystic Dysplastic Kidney (MCDK) focuses on the non-functional kidney, your child’s long-term health depends almost entirely on the other, healthy kidney [1]. Because this kidney will be doing the work of two, your medical team will pay close attention to how it grows and whether there are any other minor plumbing issues in the urinary tract.

The Healthy Kidney: Doing Double Duty

In most children with MCDK, the functioning kidney undergoes a process called compensatory hypertrophy [2]. This is a normal, healthy response where the single kidney grows larger than average to increase its filtering capacity [3].

  • Timing: This extra growth often begins before birth and continues throughout early childhood. Most children show significant enlargement of the healthy kidney by age 3 [2].
  • Significance: A larger, healthy kidney is a positive sign—it indicates the kidney is successfully taking over the work needed to keep your child healthy [3][4].

Understanding “Isolated” MCDK

Doctors often refer to MCDK as isolated. This means that the developmental glitch only affected the kidney area, and there are no other systemic health syndromes or genetic diseases [5]. However, even in “isolated” cases, it is common to find secondary anatomical issues in the urinary tract itself [6].

Vesicoureteral Reflux (VUR)

The most common secondary finding (occurring in 13% to 34% of cases) is Vesicoureteral Reflux (VUR) [6][7].

In a typical urinary tract, urine flows one way: from the kidney, down the ureter, and into the bladder. In VUR, a valve-like mechanism doesn’t close properly, allowing urine to “reflux” or flow backward from the bladder toward the healthy kidney [7].

  • Why it matters: If your child gets a bladder infection, VUR can make it easier for bacteria to travel up to the healthy kidney, potentially causing an infection or scarring [7].
  • Management: VUR is often mild and many children outgrow it. Your doctor will likely monitor for signs of a Urinary Tract Infection (UTI) and may order specific tests if UTIs become a problem [8].

The Role of Genetic Testing

In the vast majority of cases, unilateral MCDK happens by chance and isn’t linked to other health problems [5]. However, if an ultrasound shows other issues—such as anomalies in the heart, spine, or the other kidney—your doctor may recommend genetic testing [9].

  • Chromosomal Microarray (CMA): This test looks for small missing or extra pieces of DNA. In children where MCDK is the only finding, the chance of finding a genetic link is very low (about 4.8%) [10].
  • Increased Risk: If there are multiple different findings on the ultrasound, the chance of a genetic cause increases significantly, and testing can help doctors provide a clearer picture of what to expect [11][12].

Protecting the “Solo” Kidney

Because your child has one functioning kidney, the goal is to protect it for a lifetime. This generally means:

  • Routine Monitoring: Regular check-ups to track growth and blood pressure [13].
  • Quick UTI Treatment: Treating urinary infections promptly to prevent any scarring on the healthy kidney [7].
  • Staying Hydrated: Encouraging good fluid intake as your child grows.

Most children with a single healthy kidney do not need special diets or severe activity restrictions [1][14].

Common questions in this guide

What happens to the healthy kidney in a child with MCDK?
The functioning kidney naturally grows larger than average in a process called compensatory hypertrophy. This extra growth allows the single kidney to increase its filtering capacity and take over the work needed to keep your child healthy.
Does my child need genetic testing for isolated MCDK?
In most cases, isolated unilateral MCDK happens by chance and does not require genetic testing. However, if an ultrasound reveals other structural abnormalities in the heart, spine, or the other kidney, your doctor may recommend a chromosomal microarray.
What is Vesicoureteral Reflux (VUR) and why does it matter?
VUR is a condition where a valve mechanism fails, allowing urine to flow backward from the bladder toward the kidney. It frequently occurs in children with MCDK and increases the risk of bacteria reaching the healthy kidney, which can cause infections or scarring.
How can I protect my child's single healthy kidney?
You can protect the kidney by attending routine check-ups to track growth and blood pressure, encouraging good hydration, and seeking prompt treatment for any urinary tract infections. Most children with a single healthy kidney do not need severe activity or dietary restrictions.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.How much larger is the 'good' kidney than average for my child's age?
  2. 2.Is there any sign of hydronephrosis (swelling) or other structural issues in the healthy kidney?
  3. 3.Based on the ultrasound, are there any other findings that would make you recommend genetic testing?
  4. 4.What precautions should I take to protect the healthy kidney as my child starts daycare or school?

Questions For You

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References

References (14)
  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

    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
  3. 3

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

    Wang MK, Gaither T, Phelps A, et al.

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

    PMID: 30986483
  4. 4

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

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

    Journal of pediatric urology 2023; (19(5)):624.e1-624.e7 doi:10.1016/j.jpurol.2023.05.019.

    PMID: 37353361
  5. 5

    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
  6. 6

    A meta-analysis of the incidence and fate of contralateral vesicoureteral reflux in unilateral multicystic dysplastic kidney.

    Erlich T, Lipsky AM, Braga LH

    Journal of pediatric urology 2019; (15(1)):77.e1-77.e7 doi:10.1016/j.jpurol.2018.10.023.

    PMID: 30482499
  7. 7

    Necessity of performing voiding cystourethrography for children with unilateral multicystic dysplastic kidney.

    Yamamoto K, Kamei K, Sato M, et al.

    Pediatric nephrology (Berlin, Germany) 2019; (34(2)):295-299 doi:10.1007/s00467-018-4079-z.

    PMID: 30255447
  8. 8

    Voiding Cystourethrogram in Children With Unilateral Multicystic Dysplastic Kidney: Is It Still necessary?

    Blachman-Braun R, Camp MM, Becerra MF, et al.

    Urology 2020; (139()):156-160 doi:10.1016/j.urology.2020.02.005.

    PMID: 32081673
  9. 9

    Multicystic dysplastic kidneys (MCDK) during prenatal life and postnatal outcome.

    Reinhardt CJM, Henrich W, Verlohren S, et al.

    Archives of gynecology and obstetrics 2025; (312(6)):2131-2146 doi:10.1007/s00404-025-08197-y.

    PMID: 41107504
  10. 10

    Fetal Isolated Unilateral Multicystic Dysplastic Kidney Identified on Second Trimester Ultrasound: Genetic Investigation Results at a Single Referral Center.

    Jing XY, Yu QX, Xiao ZQ, et al.

    Prenatal diagnosis 2026; (46(5-6)):862-867 doi:10.1002/pd.70020.

    PMID: 41192949
  11. 11

    Prenatal diagnosis of fetal multicystic dysplastic kidney via high-resolution whole-genome array.

    Fu F, Chen F, Li R, et al.

    Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association 2016; (31(10)):1693-8 doi:10.1093/ndt/gfv465.

    PMID: 26932690
  12. 12

    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
  13. 13

    Abnormal parenchymal features in the contralateral kidney of patients with multicystic dysplastic kidney.

    Shin YS, Kim SW, Heo JE, et al.

    Pediatric nephrology (Berlin, Germany) 2026; (41(2)):369-378 doi:10.1007/s00467-025-06895-y.

    PMID: 40751813
  14. 14

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

    Hutchinson KA, Halili L, Guerra A, et al.

    Journal of pediatric urology 2021; (17(4)):556-565 doi:10.1016/j.jpurol.2021.03.001.

    PMID: 33752977

This page provides educational information about managing a healthy kidney in children with unilateral MCDK. It does not replace professional medical advice from your pediatric nephrologist or urologist.

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