American Urological Association - Medullary Sponge Kidneys


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Medullary Sponge Kidneys

Image A

Image B

  • A.k.a. Cacchi Ricci disease, characterized by multiple cysts in papillary collecting ducts of 1 or more renal pyramids.
  • Developmental defect of collecting system.
  • RET oncogene implicated, which plays a role in collecting duct development.
  • Most cases are sporadic; 5% hereditary autosomal dominance.
  • Clinical:
    • Most encountered in adults, detected incidentally on radiography during work-up for nephrolithiasis.
    • Males > females.
    • Usually bilateral.
    • May also present with hematuria, stone formation in dilated duct, obstruction, and UTI.
    • Up to 1/5 of nephrolithiasis patients reported to have MSK.
  • Radiologically, collecting ducts ectasia results to "bouquet of flower" or "bunch of grapes".
  • Gross:
    • Most cysts are <1 cm located in renal pyramids (image A) & (image B).
    • Kidneys are usually not enlarged.
  • Histology:
    • Papillary collecting ducts are dilated and lined with cuboidal or flattened epithelium.
    • Focal cellular stratification may be seen.
    • Cyst lumen may contain calculi or inflammatory cells.
    • Calculi may cause inflammation.
  • Benign course if calculi and infection are controlled.