Renal Artery Stenosis

Question 1

Definition

Answer 1

Stenosis of the renal artery (narrowing/restriction of the renal artery)

Question 2

Aetiology

Answer 2

• Atherosclerosis (older patients) - widespread aortic disease involving the renal artery ostia

• Fibromuscular Dysplasia (younger patients)
o Unknown aetiology
o May be associated with collagen disorders, neurofibromatosis and Takayasu’s arteritis
o May be associated with micro-aneurysms in the mid and distal renal arteries
(resembling a string of beads on angiography)

Question 3

Pathogenesis/Pathophysiology

Answer 3

o Renal hypoperfusion (due to the stenosis) stimulates the renin-angiotensin system leading to increased angiotensin II and increased aldosterone
o This leads to increased blood pressure
o The high blood pressure leads to fibrosis, glomerulosclerosis and renal failure

Question 4

Epidemiology

Answer 4

• Prevalence unknown
• Accounts for 1-5% of all hypertension
• Fibromuscular dysplasia occurs mainly in women with hypertension < 45 yrs

Question 5

Presenting symptoms

Answer 5

• History of hypertension in < 50 yrs
• Hypertension refractory to treatment
• Accelerated hypertension and renal deterioration on starting ACE inhibitors
• History of flash pulmonary oedema

• IMPORTANT: ACE INHIBITORS ARE BAD IN RENAL ARTERY STENOSIS

Question 6

Signs on physical examination

Answer 6

• Hypertension
• Signs of renal failure in advanced bilateral disease
• Renal artery bruits

Question 7

Investigations

Answer 7

• Non-Invasive
o Duplex ultrasound
o Ultrasound measurement of kidney size

• CT Angiogram or MR Angiography: risk of contrast nephrotoxicity
• Digital Subtraction Angiography = GOLD STANDARD

• Renal Scintigraphy
o Uses radio-agent that is either excreted by glomerular filtration or by the tubules
o Addition of an ACE inhibitor causes delayed clearance by the affected kidney (may not be useful in bilateral renal artery stenosis)