14. Cystic kidney disease

Question 1

What are the different cystic kidney diseases?

Answer 1

• Autosomal dominant polycystic kidney disease (ADPKD)
• Autosomal recessive polycystic kidney disease (ADPKD)
• Medullary cystic disease

Question 2

What is the etiology of ADPKD?

Answer 2

• Autosomal dominant mutation:
  
  • 85% - PKD1 (chromosome 16) –> ESRD by 50-years-old
  • 15% - PKD2 (chromosome 4) –> ESRD by 70-years-old
• May be clinically silent for years so family screening is very important

Question 3

What are the clinical features of ADPKD?

Answer 3

• Renal enlargement with cysts
• Abdominal pain
• Possible hematuria
• Cyst infection
• Renal calculi
• High BP
• Progressive renal failure
• Extra-renal:
  
  • Liver cysts
  • Intracranial aneurysm
  • Subarachnoid hemorrhage
  • Mitral valve prolapse
  • Ovarian cysts
  • Diverticular disease

Question 4

What is the management of ADPKD?

Answer 4

• Aggressive ttt of HTN (target <130/80)
  
  • ACEI
• Dialysis or transplantation for ESRD
• Laparoscopic cyst removal or nephrectomy in case of severe pain
• Increased water intake, decreased Na⁺ intake
• Avoid caffein

Question 5

How do you screen ADPKD?

Answer 5

• Genetic testing for PKD1 (difficult) and PKD2
• US screening
  
  • Good sensitivity and specificity depending on age
  • The following critera have good sensitivity and specificity with PPV close to 100%:
    
    • Age 18-39: >3 unilateral or bilateral cysts
    • Age 40-59: >2 cysts in each kidney
    • Age >60: >4 cysts in each kidney
• MR angiography to screen for subarachnoid bleeding in 1st degree relatives

Question 6

What is ARPKD?

Answer 6

• Autosomal recessice disease (lower prevalence than ADPKD) due to mutation of PKHD gene (chromosome 6)
• Signs are variable and many present in infancy:
  
  • Multiple renal cysts
  • Congenital hepatic fibrosis
  • Most progress to ESRD by age 15
• No specific therapy yet

Question 7

What is the medullary cystic disease?

Answer 7

• Inherited disorder with tubular loss and medullary cyst formation

Forms:

• Juvenile - AR
  
  • 10-20% accounts for 10-20% of ESRD in children
• Adult - AD
  
  • Rare

Clinical features:

• Shrunken kidneys
• Cysts in medulla
• Salt wasting
• Polyuria
• Polydipsia
• Decreased enuresis (concentration ability)
• Progresses to ESRD
• Extra-renal:
  
  • Retinal degeneration
  • Retinitis pigmentosa
  • Skeletal changes
  • Cerebellar ataxia
  • Liver fibrosis