Renal Artery Stenosis

Question 1

Define Renal Artery Stenosis

Answer 1

Narrowing of the renal artery

Question 2

Aetiology of Renal Artery Stenosis

Answer 2

Older: 
Atherosclerosis (90%)
Diabetes Mellitus
Dyslipidaemia
Smoking

Younger:
Fibromuscular dysplasia (unknown)/medial fibroplasia
Intimal and adventitial fibroplasia

Others: Post-transplant | renal artery aneurysm | Takayasu’s arteritis | atheroemboli | Williams syndrome | Neurofibromatosis | AV malformatio or fistula | renal artery dissection | trauma | abdominal radiotherapy | retroperitoneal fibrosis

Question 3

Pathogenesis or renal artery stenosis

Answer 3

Renal hypoperfusion 
→ ↑ renin-angiotensin system 
→ ↑Angiotensin II + ­ aldosterone  
→ ↑ BP with time  
→ fibrosis, glomerulosclerosis, renal failure. 

Most occurs when stenosis exceeds 50%

Question 4

Symptoms of renal artery stenosis

Answer 4

History of:
Hypertension/resistant hypertension
Flash pulmonary oedema 
Unexplained kidney dysfunction 
Multi-vessel coronary artery disease
Other peripheral vascular disease 
Kidney injury after administration of ACEi or ARB
Hypokalaemia

Question 5

Signs of Renal artery Stenosis on examination

Answer 5

Hypertension
Signs of renal failure (severe)
Abdominal bruit (heard over stenosed artery)

Question 6

Investigations for renal artery stenosis

Answer 6

Gadolinium enhanced MR angiography (MRA): >50% reduction in vessel diameter
Duplex USS: >50% reduction in vessel diameter

Urinalysis and sediment evaluation: Normal in absence of diabetic nephropathy

Aldosterone:renin ratio: <20 (excludes primary aldosteronism)

CT angiography/conventional angiography/CO2 angiography/MRA: >50% reduction