A L2.3 Renal vascular Flashcards Preview

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Flashcards in A L2.3 Renal vascular Deck (13):
1

Characteristics of the kidneys

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

2

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

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

3

Characterisation of ADPKD

  • 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)

4

Growth of ADPKD dependent on

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

5

ADPKD mutations

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

6

What is the polycystin complex?

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

7

How is renal failure characterised?

  • <500ml urine passed a day

8

Macula densa cells, granular cells, principal cells

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

9

ADPKD on renal function

  • ↓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

10

Where is renin found?

  • Juxtaglomerular A
  • Vessels
  • Cell lining cyst walls

11

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

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

12

What is RAS caused by

  • 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

13

Implication of ACE inhibitor on Renal artery stenosis

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