A L2.3 Renal vascular

Question 1

Characteristics of the kidneys

Answer 1

• Receives 20% cardiac output (~1L/min)
  
  • The more BF an organ commands, the higher the component of TPR
• Only 0.5% body weight

Question 2

Genetic features of Autosomal dominant polycystic kidney disease (ADPKD) -Genetic causes

Answer 2

• 1/700 people (common)
• 10% → no family history (could be de novo mutation/from false paternity)

Question 3

Characterisation of ADPKD

Answer 3

• Cyst formation in ductal organs
  
  • Cyst grows and crush nephrons & impairs other functions
• Early hypertension (even before kidney failure becomes a problem)
• Renal failure
• Appear in utero (before birth) & only in 1% of nephrons (but there are 1m nephrons)

Question 4

Growth of ADPKD dependent on

Answer 4

• Obstruction to nephron flow or net fluid secretion by cyst cells
• Abnormal cell proliferation
• Abnormally compliant basement membrane

Question 5

ADPKD mutations

Answer 5

• PKD1 (chrm 16) encodes polycystin-1
  
  • 85% of cases, 64 mutations
• PKD2 (chrm 4) encodes polycystin-2
  
  • 15% of cases, 50 mutations

Question 6

What is the polycystin complex?

Answer 6

• (basement membrane integrity + ion channels)
• important for cyst formation

Question 7

How is renal failure characterised?

Answer 7

• <500ml urine passed a day

Question 8

Macula densa cells, granular cells, principal cells

Answer 8

• Macula densa: baroreceptors of kidneys → signals granular cells to secrete renin
• Granular cells: secrete renin (in pre-glomerular A)
• Principal cells: responsive to aldosterone

Question 9

ADPKD on renal function

Answer 9

• ↓renal BF (compressed by cyst) BUT still maintains GFR
  
  • Post-glomerular A narrowed (sensitive to ANG) → pools blood → maintain GFR
  • Retains Na+ & H2O → ↑BP
• Renin activity is x2 higher in affected patients

Question 10

Where is renin found?

Answer 10

• Juxtaglomerular A
• Vessels
• Cell lining cyst walls

Question 11

How is renal artery stenosis (RAS) characterised - caused by environmental features

Answer 11

• Significant narrow (>70%)
• Plasma renin in 50% pop.
  
  • Suppressed by high BP
  • ↑tissue renin activity
  • Dependent on the Renin-ANG-system to function

Question 12

What is RAS caused by

Answer 12

• Atheroma (70%)
  
  • ↑resistance → ↓flow → ↓BP → detected by granular cells → activate Renin-ANG-system → maintain GFR
• Fibromuscular dysplasia (FMD) (25%) - more genetic basis
  
  • Affects young women
  • Abnormal growth in renal artery wall
  • Multiple abnormal area of obstruction in pre-kidney arteries

Question 13

Implication of ACE inhibitor on Renal artery stenosis

Answer 13

• ACE inhibitors → could cause renal failure for people with RAS
  
  • ANG inhibited → ↓BP → ↓GFR → kidney failure