Renal artery stenosis

Question 1

Define

Answer 1

• Stenosis of the renal artery

* narrowing of the renal artery lumen.

Question 2

What are the risk factors?

Answer 2

Diabetes
• Dyslipidaemia
• smoking

Question 3

What are the causes?

Answer 3

• 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 4

What’s the pathophysiology?

Answer 4

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 5

Epidemiology

Answer 5

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

RAS due to fibromuscular dysplasia is more common in women <30 years. RAS in general often presents as accelerated, resistant, or malignant HTN. RAS may be associated with acute decline in kidney function after initiation of renin-angiotensin blockade. It may be diagnosed in assessing an unexplained atrophic kidney, or discrepancy in kidney size >1.5 cm, or sudden, unexplained, and/or recurrent pulmonary oedema.

Question 6

What are the presenting symptoms?

Answer 6

• History of hypertension in < 50 yrs
• Hypertension refractory to treatment
• Accelerated hypertension and renal deterioration on starting ACE inhibitors
• History of unexplained kidney dysfunction/ history of vascular disease
• History of flash pulmonary oedema
• IMPORTANT: ACE INHIBITORS ARE BAD IN RENAL ARTERY STENOSIS

Question 7

What are the signs?

Answer 7

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

Question 8

What are the appropriate investigations?

Answer 8

• Serum creatine, potassium, urinalysis, aldosterone-to-renin ratio (<20 excludes primary aldosteronism as cause of hypertension and hypokalaemia or low-normal potassium)
• 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