Renal artery stenosis
D E F I N I T I ON
Stenosis of the renal artery.
AET IOLOGY
Main cause:
. Atherosclerosis (older patient): Widespread aortic disease involving the renal artery ostia.
. Fibromuscular dysplasia (younger patient): Fibromuscular dysplasia is of unknown aetiology
but may be associated with collagen disorders, neurofibromatosis and Takayasu’s
disease. This may be associated with micro-aneurysms in the mid and distal renal arteries
(resembling string of beads on angiography).
E P IDEMI OLOGY
Prevalence is unknown but believed to account for 1–5% of all hypertension;
fibromuscular dysplasia occurs mainly in women with hypertension at <45 years.
H ISTORY
History of hypertension in <50 years.
Hypertension refractory to treatment.
Accelerated hypertension and renal deterioration on starting ACE inhibitor.
History of flash pulmonary oedema.
EXAMI N A T ION
Hypertension.
Signs of renal failure in advanced bilateral disease.
An abdominal bruit may be heard over the stenosed artery.
PATHOLOGY/PATHOGENESI S
Renal hypoperfusion stimulates the renin-angiotensin
system leading to " circulating angiotensin II and aldosterone, increasing BP, which in
turn, with time, causes fibrosis, glomerosclerosis and renal failure.
I N V E S T IGATIONS
Non-invasive: Duplex ultrasound (technically difficult if obese). Ultrasound
measurement of kidney size (predicts outcome after revascularization, kidneys
<8 cm are unlikely to improve).
CT angiography or MRA: Often used now; risk of contrast nephrotoxicity.
Digital subtraction angiography: Gold standard assessment.
Renal scintigraphy: Uses the radio-agent 99Tc-DTPA (excreted by glomerular filtration) or
99Tc -MAG3 (excreted by tubules). Addition of an ACE inhibitor (captopril
renography) causes delayed clearance by the affected kidney (may not be helpful if
bilateral RAS).
MANAGEMENT
Medical: Pharmacological control of hypertension. In atherosclerotic
cases, medical treatment is often preferred together with modulation of other cardiovascular
risk factors. Avoidance of ACE inhibitors and other nephrotoxic agents.
Intervention: In cases of uncontrolled hypertension, progressive renal failure, flash pulmonary
oedema, stenoses >60%.
Angioplasty þ/stenting: Treatment of choice for fibromuscular dysplasia, less effective in
atherosclerotic cases.
Surgical revascularisation: Several approaches are used, e.g. aortorenal bypass using saphenous
vein or synthetic grafts (PTFE or Dacron), aortic replacement and renal reconstruction,
endarterectomy of atherosclerotic RAS, extra-anatomical bypass (hepatorenal on
right, splenorenal on left).
COMPL I C A T IONS
Drug-refractory hypertension, renal failure.
Of angioplasty: Restenosis (occurs in up to 20%), rarely renal artery rupture or thrombotic
occlusion may require emergency surgery (with high mortality 40%).
P ROGNOS I S
Untreated hypertension will progress to renal failure. With intervention
50–70% will have improvement in BP and renal function. Curative in 15%.
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