Hypertensive Renal Disease

Question 1

Causes of renal artery stenosis

Answer 1

• Atherosclerotic disease (60-80%) → >55 years, prevalence increases w/ age, M=F, risk relates to burden of other CVS risk factors, ostial/proximal portion of renal artery, can be B/L, ischaemic atrophy/total occlusion common, less amenable to intervention
• Fibromuscular dysplasia (10-20%) → non-atheromatous, non-inflammatory, +ve family history in 7%, F:M 3:1 age 35-50, mid to distal renal artery (string of beads). Risk increased w/ smoking, pregnancy. Can affect multiple vascular beds (carotids, peripheral arteries). Ischaemic atrophy/total occlusion rare. Very amenable to intervention.
• Other:
  
  • Renal artery embolism
  • Dissection/thrombosis
  • Post-traumatic injury
  • Occlusion from aortic stent graft
  • External compression
  • Systemic vasculitis

Question 2

Pathogenesis of Renovascular Hypertension

Answer 2

• Increasing stenosis → reduction in post-stenotic blood flow and pressure → activates RAAS
  
  • Need approx 80% stenosis to see changes in flow/pressure and subsequent activation of renin

Question 3

When to suspect renovascular disease/hypertension

Answer 3

• Age of onset <30 or > 50
• Abrupt onset hypertension
• Acceleration of previous stable BP
• Malignant hypertension
• Accelerated retinopathy
• Flash pulmonary oedema
• AKI with ACEi

Question 4

Diagnosis of renal artery stenosis

Answer 4

• Renin and aldosterone levels - low sensitivity and specificity
• Doppler ultrasound - good screening test (sensitivity 97%, specificity 81%) → no contrast/radiation, operator dependent, does over-estimate degree of stenosis, cannot accurately determine degree of stenosis in FMD
• CT Renal angiogram → good images, can detect accessory vessels, less accuracy in advanced CKD due to calcification, may be useful for assessing stent patency c/w MRI
• MRI Renal angiogram → Sensitivity 92-97%, specficity 73-93%, risk of gadolinium nephrogenic systemic fibrosis in CKD
• Nuclear ACEI Scintigraphy → sensitivity >75%, specificity >90%. Administration of ACEi → reduction in efferent vascular tone, if fixed lesion in afferent vessel GFR will drop. Functional assessment not anatomic.
• Angiography → gold standard, reserved for confirmation of diagnosis. Risks → AKI, cholesterol emboli, contrast induced nepropathy, dissection, groin haematoma

Question 5

Medical therapy for renal artery stenosis

Answer 5

• Blood pressure management → RAAS blockade, multimodal therapy may be required
  
  • RAAS blockade >90% tolerated without AKI. Also risk reduction for death
• CVS risk factor modification
  
  • Lipid and diabetes
  • Smoking cessation, weight loss, salt intake reduction
  • Anti-platelets (where indicated for other vascular disease)

Question 6

Role of angioplasty in renal artery stenosis

Answer 6

• FMD → cure with angioplasty and stent, can re-occur w/ benefit from re-intervention also
• Atherosclerotic → conclusions from ASTRAL & CORAL angioplasty +/- stenting no superior to medical treatment in those with mild to moderate disease w/ respect to BP control and clinical event endpoints but did not address high risk populations (advancing renal impairment, flash APO). Possible role in high risk disease.

Complications of stenting

• Groin haematoma
• Segmental infarction, perineprhic haematoma, renal artery thrombosis/occlusion, stent misplacement , dissections, embolisation