Classification of Cystic Diseases

Classification of Cystic Diseases

Helen Liapis, MD

Joseph Gaut, MD, PhD

Adult ADPKD kidneys are massively enlarged and contain numerous oval/spherical cysts dispersed throughout the cortex and medulla. Cysts are lined by thin walls; some contain hemorrhagic fluid image.

Early onset ADPKD in a young child shows oval cysts varying in size, filled with turbid gelatinous fluid image. Overall size of the kidney is moderately large for age.



  • Renal diseases characterized predominately by cysts

    • Cyst: Closed cavity in a previously noncystic structure

      • Cysts may arise in any part of nephron, but most frequently in tubules

      • Cysts may be found in renal cortex, medulla, or both

      • Cysts may be diffuse, focal, unilateral, or bilateral

      • Bilateral cysts are most commonly hereditary

      • Cysts can be randomly or uniformly distributed (e.g., along corticomedullary junction)

      • Sometimes ectasia is present rather than a closed cyst

    • Cysts arising in glomeruli are called glomerular cysts

    • Term “polycystic” should only be used for autosomal dominant and autosomal recessive polycystic kidney disease (ADPKD, ARPKD)

    • Location and shape of renal cysts are important for classification

    • No universally accepted classification scheme

    • Features considered

      • Genetic basis

      • Cystic anatomic structure (tubule, glomerulus, other)

      • Distribution of cysts (cortex, medulla)


  • Hereditary cystic diseases

    • Autosomal dominant polycystic kidney disease (ADPKD)

    • Autosomal recessive polycystic kidney disease (ARPKD)

    • Medullary cystic kidney disease (MCKD)

    • Nephronophthisis (NPH)

    • Tuberous sclerosis (TSC)

    • von Hippel-Lindau (VHL) disease

    • Primary glomerulocystic kidney disease (GCKD)

  • Acquired cystic diseases

    • Secondary GCKD

    • Acquired cystic disease (end-stage kidney)

    • Medullary sponge kidney

    • Multilocular renal cyst

    • Simple cortical cyst

  • Non-nephron renal cystic diseases

    • Pyelocalyceal diverticula

    • Perinephric pseudocyst

    • Lymphangiectasis/lymphangiomatosis



  • ADPKD: 1 in 500 live births

  • ARPKD: 1 in 20,000 live births

  • NPH: 1 in 8,000,000 in USA, 1 in 50,000 in Canada

  • TSC: 1 in 10,000-15,000 live births



  • Cystogenesis: Process involving aberrant formation or maintenance of a normally noncystic structure

  • Causes of tubular cysts

    • Epithelial cell proliferation

    • Apoptosis and defective clearance of apoptotic cells causing tubular obstruction

    • Scarring of tubule due to inflammation, injury and fibrosis with consequent obstruction

    • Expansion of luminal contents by vectorial fluid/solute shift

      • Electrolyte contents reveal distal or proximal tubular transport function

    • May begin as an ectatic tubule that later becomes a closed cystic space

  • Causes of glomerular cysts unclear

    • May involve scarring of outlet

    • Failure of normal proximal tubule formation


Differential Diagnostic Features

  • Spherical cysts in bilaterally enlarged kidneys are diagnostic of ADPKD

  • Cylindrical cysts (really ectatic collecting ducts) in enlarged pediatric kidneys are diagnostic of ARPKD

  • A few small cysts at corticomedullary junction are characteristic of NPH

  • Isolated cortical cysts, usually unilateral, are nonhereditary, simple cysts seen in elderly patients with no renal disease


Differential Diagnostic Features

  • Cysts contain abundant eosinophilic fluid and micropapillary proliferations characteristic of ADPKD

  • Cylindrical cysts are characteristic of ARPKD

  • Glomerular cysts affecting > 5% of glomeruli define glomerulocystic kidney disease as being either primary or secondary

  • Secondary GCKD is more common than primary and presents in children with ADPKD, ARPKD, or TSC

    • Glomerular cysts are defined as Bowman capsule dilation > 3x normal

  • Cysts containing renal cell carcinoma are characteristic of hereditary neoplasia syndromes (TSC, von Hippel-Lindau disease) ADPKD, or hemodialysis-induced cysts

  • Cysts in NPHP/MCDK form are ex vacuo (degenerative); may contain Tamm-Horsfall protein and show tubular basement membrane duplication

  • Incidental, simple cysts are also degenerative and often lack epithelial lining



  • Classic ADPKD in adults

  • Early onset ADPKD in children

Jul 7, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Classification of Cystic Diseases

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