Reno- vascular Disease

Question 1

ischaemic nephropathy

Answer 1

reduced glomerular filtration rate caused by reduced renal blood flow beyond the levels of auto-regulatory compensation over time can cause renal atrophy and progressive chronic kidney disease

Question 2

causes of ischaemic nephroapthy

Answer 2

• essential hypertension

- secondary hypertension caused by renovascular disease

Question 3

renovasuclar disease caused by

Answer 3

• atherosclerosis of the renal artery

- or fibromusuclar dysplasia

Question 4

renal artery stenosis

Answer 4

narrowing of the renal artery causing reduced perfusion of the kidney which is sensed by the kidney which then tries to raise blood pressure throughout the body

Question 5

where the distal convoluted tubules passes the glomerulus

Answer 5

is the location of the juxtaglomerular cells which are wrapped around the endothelial cells of the afferent arteriole

Question 6

the juxtaglomerular cells

Answer 6

are specialised smooth muscle cells which secrete renin in response to low blood pressure

Question 7

there are also what cells close to the distal convoluted tubules

Answer 7

macula densa cells which are chemoreceptors which sense the NaCl concentration in the tubules, if blood pressure falls then less NaCl is in the tubules which is sensed by the macula densa cells which send out a local prostaglandin signal which reaches the junta-glomerular cells causing them to release renin

Question 8

in addition the juxtaglomerular cells can

Answer 8

directly sense low pressure in the afferent arteriole and also repond to sympathetic nerve fibres to release renin

Question 9

renin helps to

Answer 9

constrict blood vessels and increase sodium re-absorption in the nephrons causing increased blood pressure which then stops the just-gloermualr cells releasing renin so balance is restored

Question 10

atherosclerosis causing renal artery stenosis

Answer 10

• mostly occur in over 50s
• more common in males
• usually unilateral
• rarely just affects the renal artery usually occurs in other arteries i.e. the coronary arteries

Question 11

another cause of renal artery stenosis is

Answer 11

renal fibromuscular dysplasia which is caused by a problem of the smooth muscle and the connective tissue in the walls of the renal artery

Question 12

fibromuscular dysplasia

Answer 12

• most common in females between the ages of 15-50
• familial in 10% of cases and tends to be bilateral
• associated with other hereditary conditions such as ehlers dahnlons syndrome
• can involve cerebral arteries and cause a carotid artery dissection

Question 13

in fibromuscular dysplasia the renal artery looks like

Answer 13

a string of beads

Question 14

in both atherosclerosis and fibrouscular dysplasia

Answer 14

the renal artery narrows so the blood pressure within the kidneys is low causing the release of renin from the juxtaglomerular cells which increases the systemic blood pressure but the pressure within the kidney remains low because of the obstruction so there is the constant release of renin causing hypertension

Question 15

in affected kidneys

Answer 15

they are receiving less blood than usual so they eventually atrophy

Question 16

if only one kidney is affected the

Answer 16

other kidney can compensate

Question 17

but if both kidneys are affected it can cause an

Answer 17

AKI

Question 18

presentation of renal artery stenosis

Answer 18

• headaches and blurry vision caused by the hypertension
• abdominal bruits
• flash pulmonary oedema

Question 19

diagnosis of renal artery stenosis

Answer 19

CT angiography or MRI angiography

Question 20

on CT or MRI angiography

Answer 20

• atherosclerosis tends to affect the initial portion of the renal artery whereas, in fibromusuclar dysplasia the narrowing occurs in the mid to distal renal artery

Question 21

treatment of renal artery stenosis caused by atherosclerosis

Answer 21

• statins, anti-platelets, hypertension control

Question 22

whats important about ACE inhibitors in renal artery stenosis

Answer 22

they are absolutely contraindicated in bilateral renal artery stenosis because they inhibit the production of angiotensin II causing vasodilation of the efferent arteriole (angiotensin II normally causes vasoconstriction of the efferent arteriole, in renal artery stenosis the afferent arteriolar pressure is low therefore, autoregualtion of the GFR is dependant on changes in the tone of the efferent arteriole, but if no angiotensin II is produced then autoregualtion is impaired GFR falls and renal failure will occur

Question 23

radiological interventions in renal artery stenosis

Answer 23

angioplasty +/- stenting (fibromsuclar dysplasia responds extremely well to interventional radiology as it resolves the hypertension)