Renal Artery Stenosis

Question 1

def

Answer 1

narrowing of the renal artery lumen

Question 2

when is narrowing of the renal artery lumen considered significant

Answer 2

> 50% reduction in vessel diameter

Question 3

what occurs as a result of renal artery narrowing

Answer 3

ischaemic nephropathy

Question 4

what is renovascular HTN

Answer 4

HTN mediated through high levels of renin and angiotensin II

these are produced in high amounts with an underperfused kidney by a stenosed renal artery

Question 5

epi

Answer 5

notable cause of HTN and ESRD

Question 6

what are the two common causes of RAS

Answer 6

1 atherosclerotic RAS (most common)

2 fibromuscular dysplasia

Question 7

what is atherosclerotic RAS associated with

Answer 7

atherosclerosis (CAD)
DM
dyslipidaemia
smoking

Question 8

what is dyslipidaemia

Answer 8

high LDL or low HDL

Question 9

what are less common causes of RAS

Answer 9

post transplant
arteriovenous malformations (hyperthyroidism)
trauma

Question 10

what does RAS do to renin and sodium

Answer 10

decreased perfusion to the kidneys leads to increased production of renin which is used to convert angiotensinogen into angiotensin I where ACE is used to convert it into angiotensin II
angiotensin II causes SM constriction leading to HTN and aldosterone synthesis leading to Na and water retention (which adds to HTN)

Question 11

which part of the renal artery does atherosclerotic RAS affect

Answer 11

proximal third

Question 12

which part of the renal artery does fibromuscular dysplasia affect

Answer 12

distal 2/3rds

Question 13

risk factors

Answer 13

dyslipidaemia (leads to atherosclerosis and atherosclerotic RAS)
smoking (associated with both atherosclerotic RAS and fibromuscular dysplasia)
DM (atherosclerotic RAS)

Question 14

history

Answer 14

headaches if severe HTN

SOB due to pulmonary oedema

Question 15

examination

Answer 15

Hx of HTN, kidney problems, and CAD or PVD
renal artery bruit
pulmonary oedema

Question 16

what does HTN <30yrs suggest about the cause of RAS

Answer 16

fibromuscular dysplasia

Question 17

investigations

Answer 17

1 bloods
-UEs (high creatinine, low K + high Na (due to activation of the renin-angiotensin system))
2 urinalysis
-no proteinuria
3 aldosterone-to-renin ratio
-if <20 excludes primary aldosteronism

Question 18

what does HTN >55yrs suggest about the cause of RAS

Answer 18

atherosclerotic RAS

Question 19

what conditions increase likelihood of atherosclerotic RAS

Answer 19

CAD, PVD

Question 20

a 68y/o man with known CAD + PVD presents with recurrent episodes of pulmonary oedema (SOB), worsening kidney function, progressively difficult-to-control HTN, an angiogram shows a sclerotic aorta with a plaque extending to the proximal third of both renal arteries

Answer 20

atherosclerotic RAS

Question 21

a 32y/o woman with no PMH presents with headaches and is found to have HTN. Her BP responds inadequately to thiazide diuretics and CCBs. An MRA of renal arteries shows a beaded appearance indicative of fibromuscular dysplasia

Answer 21

fibromuscular dysplasia