Multicystic Dysplastic Kidney

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DESCRIPTION

  • A multicystic dysplastic kidney (MCDK) is the most severe type of cystic renal dysplasia and is characterized by multiple noncommunicating macroscopic cysts and not working renal tissue.
  • In general, an MCDK does not filter or produce urine and thus children with unilateral MCDK effectively have a solitary kidney.
  • In some children, an MCDK is associated with decreased glomerular filtration rate (GFR) and chronic kidney disease (CKD), suggestive of a contralateral dysplastic kidney.
  • Bilateral MCDK
    • Severe impairment of fetal kidney function typically results in oligohydramnios or anhydramnios associated with pulmonary hypoplasia and high rates of perinatal mortality.
    • If neonate survives, he or she would need kidney replacement therapy after birth. Prenatal and postnatal evaluation by pediatric nephrology and urology is needed.

EPIDEMIOLOGY

  • Incidence is 1 in 4,300 live births.
  • More common in boys than in girls
  • Can occur on either side
    • Usually unilateral and isolated
    • Left MCDK is more common than right.
    • Rare bilateral MCDK occurs with an incidence of 1 in 10,000 live births.

RISK FACTORS

  • Unilateral or bilateral MCDK is generally sporadic.
  • Familial forms of MCDK are associated with up to 50% recurrence risk.
  • Chromosomal abnormalities (copy-number variants with microdeletions or duplications) may be detected by array comparative genomic hybridization (aCGH) in up to 30% of MCDK.
  • MCDK may be associated with mutations in kidney developmental genes including HNF1B, ACE, PAX2, REN, ROBO2, AGTR1, SALL1, and AGT.

PATHOPHYSIOLOGY

  • Not fully understood but may be due to the following:
    • Impaired signaling between ureteric bud and metanephric mesenchyme with defective mesenchymal-epithelial transition in early stages of kidney development
    • Ureteral obstruction during fetal kidney development
  • On histology, MCDK are characterized by cysts lined by flattened cuboidal epithelium. The stroma between cysts is fibrotic with mesenchymal components, immature glomeruli, primitive tubules, and nerve bundles as well as dysplastic ducts.

COMMONLY ASSOCIATED CONDITIONS

  • Associated anomalies of the contralateral genitourinary (GU) tract include the following:
    • Vesicoureteral reflux (VUR): most common, occurs in ~20%
    • Renal hypoplasia or dysplasia
    • Ureterocele
    • Ureteropelvic junction (UPJ) obstruction
    • Genital anomalies
  • Extrarenal malformations may include cardiac, central venous system, gastrointestinal, or skeletal abnormalities.

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