Renal Artery Stenosis

Question 1

What is renal artery stenosis?

Answer 1

narrowing of the renal artery lumen

Question 2

Give 2 main causes of RAS

Answer 2

Atherosclerosis (older patients)
Fibromuscular Dysplasia (younger patients)

Question 3

Describe the aetiology of atherosclerosis causing RAS

Answer 3

Widespread aortic disease involves renal artery ostia

Question 4

Describe the aetiology of Fibromuscular Dysplasia causing RAS

Answer 4

Unknown aetiology
May be associated with collagen disorders, neurofibromatosis + Takayasu’s arteritis
May be associated with micro-aneurysms in the mid + distal renal arteries

Question 5

Describe the pathophysiology of RAS

Answer 5

Renal hypoperfusion (due to stenosis) stimulates the renin-angiotensin system leading to increased angiotensin II + increased aldosterone
Leads to increased BP
High BP leads to fibrosis, glomerulosclerosis + renal failure

Question 6

Describe the epidemiology of RAS

Answer 6

Prevalence unknown
1-5% of all HTN
Fibromuscular dysplasia occurs mainly in F with HTN < 45 yrs

Question 7

What may feature in the history of a patient presenting with RAS?

Answer 7

Hx of HTN in < 50 yrs
HTN refractory to tx
Accelerated HTN + renal deterioration on starting ACEi
Hx of flash pulmonary oedema

Question 8

What non invasive investigations may be performed in RAS?

Answer 8

Duplex ultrasound
Ultrasound measurement of kidney size
CT Angiogram or MR Angiography: risk of contrast nephrotoxicity
Digital Subtraction Angiography = GOLD STANDARD

Question 9

What other investigations may be performed in RAS?

Answer 9

Renal Scintigraphy
Uses radio-agent that is either excreted by glomerular filtration or by the tubules
Addition of an ACEi causes delayed clearance by the affected kidney (may not be useful in bilateral RAS)

Question 10

Give 3 risk factors for RAS

Answer 10

Hyperlipidaemia
Smoking
Diabetes

Question 11

What may RAS resemble on angiography?

Answer 11

String of beads