CUA: Multicystic Dysplastic Kidney in the Neonate (2015)

See Original Guideline

Epidemiology

• Unilateral MCDK is a common condition (1/4300 live births)

Pathogenesis

• Results from the abnormal differentiation of the metanephric parenchyma during early embryologic development of the kidney
  • Most renal cystic conditions whether congenital, acquired, or sporadic arise from the nephrons and collecting ducts after they have formed.
    • MCDK is an exception in that it arises prior to formation of the nephron.

Classification: “Simple” vs. “Complex”

• “Simple” (3):
  1. Unilateral dysplasia with
  2. Normal contralateral kidney with compensatory hypertrophy and
  3. No GU abnormalities detected by US or physical examination
• “Complex” (3):
  1. Bilateral dysplasia or
  2. Abnormalities of the contralateral kidney or
  3. Abnormalities of the GU detected by US or physical examination

Diagnosis and Evaluation

• Generally asymptomatic at presentation
• Medical conditions associated with MCDK
  1. Hypertension
     • Routine blood pressure should be performed on children with MCKD
       • If hypertension is identified, it should be appropriately managed
         • Nephrectomy may cure the HTN if no other etiologies are identified
  2. Chronic renal insufficiency/end-stage renal disease
     • The contralateral kidney in those with
       • “Simple” MCDK does not warrant urological follow-up, but does warrant nephrological follow-up
         • The compensatory hypertrophy of the contralateral kidney in children born with a congenital solitary functioning kidney, previously seen as reassuring for preserved renal function, may reflect glomerular hypertrophy, and can lead to hyperfiltration injury which may be marked by HTN and proteinuria. As such, long-term follow-up of this nephrological issue is recommended
         • Children with a normal solitary functioning kidney, with evidence of compensatory hypertrophy, have a small risk of future renal insufficiency (risk of CRF or ESRD at 5 years is negligible)
       • “Complex” MCDK warrants urological and/or nephrological follow-up, depending on the associated abnormalities identified
         • In “complex” MCDK, the risk of CRF and ESRD at 7 years is 29% and 21%, respectively
     • Parents of children with a solitary functioning kidney should be counselled on the issue of sports and the solitary kidney
  3. Urinary tract infection and vesicoureteric reflux
     • “Simple” MCDK has the lowest risk of UTI; “complex” MCDK has the highest risk of UTI
       • The risk of UTI over 5 years is 7% in “simple” MCDK, 29% in “complex” MCDK
     • The overall incidence of contralateral VUR is higher in those with MCDK than the general population.
       • The likelihood of having MCDK associated contralateral VUR is significantly higher in those whose US shows contralateral renal abnormalities when compared to those whose do not; however, when the only contralateral anomaly is hydronephrosis, the likelihood of having MCDK associated contralateral VUR is not significantly different from those with a completely normal contralateral kidney
     • The decision to perform a VCUG should take into consideration the risks of the child having VUR and developing a UTI
  4. Anomalies of the internal genitalia
     • The co-existence of renal and reproductive duct anomalies is well established
       • 26% of men with unilateral congenital absence of the vas deferens (CAVD) and 11% of men with bilateral CAVD had an absent ipsilateral kidney
       • Uterus didelphys and obstructed hemivagina have an increased association with ipsilateral renal agenesis
     • Females with MCDK should have a screening pelvic US at puberty
     • The role of screening in male for anomalies of the genital ducts is unclear
     • Any recommendations that refer to the assessment of the internal genitalia in patients with a congenital solitary kidney, should be applied to patients with a history of a MCDK
  5. Wilms tumor
     • The increased risk of developing WT appears negligible, if not nonexistent, and does not warrant surveillance
  6. Renal cell carcinoma and other adult renal malignancies
     • There is a very low risk of an adult malignancy developing in a MCDK; there is no evidence to suggest that this risk is higher in MCDKs that have failed to undergo radiographic involution

Management

• Initial management remains non-surgical
• The main controversy revolves around the appropriate intensity and length of US follow-up
  • As the child ages, the condition becomes less urological and more nephrological
  • MCDK is not felt to be a problem identified in adults

Recommendations – the role of the urologist

1. Confirm the diagnosis of MCDK is correct
   • US criteria are clear: lobulated renal contour with multiple internal cysts of varying sizes and shapes: the renal parenchyma is usually fibrous and echogenic with absent or small hilar vessels. The cysts typically cluster and are non-communicating.
2. Use of clinical judgement to determine if VCUG is indicated to identify VUR (see above)
3. Determine if MCDK is “simple” or “complex” and manage accordingly
   • “Complex” MCDK warrants urological and/or nephrological follow-up, depending on the associated abnormalities identified
     • Annual blood pressure monitoring and screening for proteinuria should be included in follow-up
   • Confirmation of “simple” MCDK warrants a repeat US at 12–24 months to confirm compensatory hypertrophy
     • Those with “simple” MCDK do not warrant further urological follow-up
     • Discharge from urological follow-up should include:
       • Determining locally if the child should have ongoing follow-up by pediatric nephrology or their primary care physician for blood pressure monitoring and signs of hyperfiltration (proteinuria and decreased renal function)
4. Recommendation of a screening pelvic US for females following advanced puberty, with referral to a gynecologist if anomalies are identified
5. Counselling the parents on sports and the solitary kidney

Questions

1. Contrast simple vs. complex MCDK.
   • Simple: unilateral dysplasia with contralateral normal kidney with compensatory hypertrophy and no GU abnormalties
   • Complex: bilateral dysplasia or abnormal contralateral kidney or presence of GU abnormalities
2. Which medical conditions are associated with MCDK?
   1. HTN
   2. CKD
   3. UTI
   4. VUR
   5. Anomalies of internal genitalia
3. Describe the follow-up of a patient with MCDK
   • Simple: US at 12-24 months to confirm compensatory hypertrophy, of okay, follow-up nephrology for assessment of BP and proteinuria
   • Complex: annual assessment of BP and proteinuria +/- imaging
   • Consider VCUG to r/o VUR
   • Pelvis US at puberty in females

Answers

1. Contrast simple vs. complex MCDK.
   • Simple: unilateral dysplasia with contralateral normal kidney with compensatory hypertrophy and no GU abnormalities
   • Complex: bilateral dysplasia or abnormal contralateral kidney or presence of GU abnormalities
2. Which medical conditions are associated with MCDK?
   1. HTN
   2. CKD
   3. UTI
   4. VUR
   5. Anomalies of internal genitalia
3. Describe the follow-up of a patient with MCDK
   • Simple: US at 12-24 months to confirm compensatory hypertrophy, of okay, follow-up nephrology for assessment of BP and proteinuria
   • Complex: annual assessment of BP and proteinuria +/- imaging
   • Consider VCUG to r/o VUR
   • Pelvis US at puberty in females