Renal Artery Stenosis

Question 1

Renal artery stenosis leads to ___ of the kidneys

Answer 1

ischemia of the kidneys. basically like atherosclerotic kidney disaese. caused by metabolic risk factors, in older people. often evidenced by other peripheral arteries

Question 2

two types of stenosis that can happen to the artery of the kidney

Answer 2

1. atherosclerotic narrowing
2. fibromuscular dysplasia

Question 3

t/f fibromuscular dysplasia is often caused by metabolic risk factosrs,l ike atheroscleotic kidney diseas

Answer 3

dalse. its uaully genetic, resulting indysplastic or hypertrophic changes. seen in YOUNGER women under 60, vs in AKD where it affects OLDER people.

Question 4

note: presentation depends on whether the kidney narrowing is ____ or ___

Answer 4

uniterlateral or bilateral

Question 5

general mechanism of unilateral renal artery stenosis

Answer 5

unilateral renal artery stenosis. usually narrowed by 60% of the lumen, resulting in hypoxia and the activation of the RAAS system.

Activation of the RAAS system causes salt and water retention, leading to hypertension. in unilateral renal artery stenosis, HYPERTENSION IS THE PRIMARY FEATURE. Hypertension secondary to kidney disease is evidenced in people less than 30

Question 6

mechanism of bilateral renal artery stenosis and main presentations

Answer 6

bilateral renal artery stenosis: both arteries are narrowed by 60% or more. HYPERTENSION AND FLASH PULMONARY EDEMA due to excessive salt retenion and diastolic dysfunction is commonly seen.

Question 7

explain how the change in creatinine after being started on an ACE/ARB can indicate bilateral renal artery stenosis

Answer 7

normally, when ACE is started, creatining may rise, but BY LESS THAN 20%.

• if createinine rises >30%, then bilateral RAS is suspected.
  recall: the gfr is determined by the inflow of the afferent arteirole, and the outflow of fthe efferent arteriole pressure. If blood flow is reduced via narrowing to renal artery, the efferent arteriole will CONSTRICT because of activation of the raas system in an attempt to maintain a GFR.

giving an ACEi/ARB causes the efferent arteriole to DILATE. Since the afferent arteriole is still narrowed, the gfr will drop precipitously. this doesn’t happen for UNILATERAL artery stenosis because the good kidney can compensate for the fall int he GFR.

Question 8

if the gfr is rapidly falling, is this more indicative of bilatral or unilateral RAS.

Answer 8

• ongoing ischemia to both kidneys result in scarring adn kidney function loss. if dropping rapidly without explaination, consider bilateral ischemeia of the kidney.

Question 9

key physical exam finding for renal artery stenosis (in addition to flash edema and hypertension)

Answer 9

systolic and diastolic lateralizing buit are HIGHLY SPECIFIC for renal artery stenosis.

Question 10

what is done to definitively confirm Renal arteyr stenosis

Answer 10

KUB ultrasound, or duplex ultrasound– its better because no contrast is needed..

• CT angiography is highly sensitive and specific. high radiation and injection of contrast may be unsafe in CKD.

Question 11

T/F fibromuscular dysplasia can be picked up on MR angiography

Answer 11

false. unreliable in FMdysplasia

Question 12

gold standard imaging for diagnosing RAS

Answer 12

angiography.

• it is invasive and only reseved for intervention.

Question 13

Question 14

general management of RAS

Answer 14

ACE/ARB for UNILATERAL (recall that in bilateral RAS it can cause a rise in creatinine and lower the GFr even further by dialting the efferent arteriole.

• DASH diet
• statin
• ASA
• smoking cessation

Question 15

when is angioplasty considered?

Answer 15

usually for fibromuscular dysplasia. if RAS is due to athersclerosis, it’s often treated with BP control, lifestyle changes nad vascular risk protection.

• in both types of RAS, it’s critical for hypertension managment to occur.