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Renal Dysplasia

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  • Abnormality of metanephric differentiation during embryonic development characterized by disorganized abnormal immature or primitive structures in kidney.
  • Suggested to be a defect in inducer tissue (ureteric bud) and responding tissue (metanephric blastema) interactions.
  • Syndromes: Usually sporadic but may be associated with hereditary syndromes involving multiple malformations.
  • 90% have associated ureteral abnormality including obstruction, agnesis or atresia and lower urinary tract abnormalities (ureterocele or posterior urethral valves).
  • >50 have contralateral kidney defects.
  • Gross:
    • Cystic kidneys, which may be segmental, unilateral, or bilateral (image A) & (image B).
    • Randomly distributed multiple cysts.
    • Kidney not reniform shape.

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  • Histology: 3 classic features:
    • "Cuffs" of spindle cells around primitive or fetal-appearing tubules (image C).
    • Islands of metaplastic cartilage (30%) (image D).
    • Loss of normal renal architecture.
    • Frequently segmental in adults and diffuse pattern in pediatrics.
    • Decrease number in nephron.
  • Good prognosis if unilateral.