Renal vascular disease + Angiotensin 2 blockers Flashcards
What is renal vascular disease?
The name given to a variety of complications that affect the arteries and veins of the kidneys
The most common is renal artery stenosis
What is renal artery stenosis?
Narrowing if the artery supplying the kidneys
Considered angiographically significant if more that 50% of the lumen diameter is lost
What are the consequences of renal artery stenosis?
Renovacular hypotension
Activation of RAAS and thus hypertension
Ischaemic nephropathy - GFR is chronically reduced due to a lack of blood flow to the kidney
Discuss the epidemiology of renal artery stenosis
- 2-5% prevalence in hypertensive patients
- Atherosclerotic RAS accounts for 90% of cases
- Prevalence is as high as 25% of patients with coronary artery disease undergoing cardiac catheterisation
- 10% of RAS cases are caused by fibromuscular disease
What is fibromuscular RAS?
Non-atherosclerotic, non-inflammatory disease of the blood vessels that causes abnormal growth within the wall of an artery (most commonly the renal and carotid arteries)
Affects females 2-10x more than males
Caused by medial fibroplasia in 90% of cases (tunica intima and adventitia are less commonly affected)
Outline some causes of renal artery stenosis
- Atherosclerosis (90%)
- DM
- Dyslipidemia
- Smoking
- Post transplant
What is takayasu’s arteritis?
Granulomatous inflammation of major blood vessels
Most commonly in the aorta but can affect kidneys
Most common in younf or middle aged Asian women
Discuss the link between angiotensin 2 and renovascular disease
Hypoperfusion of kidneys = RAAS activation
Angiotensin 2 stimulates fibroblast activity which causes fibrosis in renal tubules
Ang 2 also stimulates the adrenal cortex to produce aldosterone which is a powerful vasocinstrictor
Ang 2 mediates constriction of the efferent arteriole of the glomerulus to increase filtration pressure - is the setting of renal vascular disease, pressure in the glomerulus is low because it is the arterial constriction and not the afferent constriction that lowers the pressure within the nephron. By using ACEi/ ARBs, the ability for ang 2 to promote an increase in GFR is lost - meaning the nephron is hypoperfused and nephropathy occurs
Outline the affect of various exogenous/ endogenous compounds on the afferent and efferent arterioles
How can renal artery stenosis be classified?
Anatomically: bilateral, unilateral, proximal, distal
Severity: moderate (50-70% occlusion), severe (>70% occlusion), total occlusion
What are the risk factors for renal artery stenosis?
Smoking
Dyslipidemia
Diabetes
Female (although a weak risk factor)
What are the common diagnositc factors of renal artery stenosis?
- Onset of hypertension
- Treatment of resistant hypertension
- Hx of unexplained renal dysfunction
- Multi-vessel coronary artery disease
- Hx of PVD
- Abdo bruit
- Sudden or recurrent pulmonary oedema
How can renal artery stenosis be managed?
- Control risk factors e.g. smoking and diabetes
- Aspirin _ statin
- Surgery is reserved for patients with other vascular disease e.g. AAA
- ACEi/ ARBs, if given, require GP follow-up or BP, GFR and electrolytes
How can fibromuscular RAS be managed?
1st: antihypertensives + lifestyle + percutaneous renal artery balloon angioplasty
2nd: surgical reconstruction of the renal arteries is restricted to patients undergoing major aortic reconstruction for another reason + renal artery stenting + dual anti-platelet surgery
