17. Microvascular complications

Question 1

what are the common sites of microvascular complication?

Answer 1

• retinal arteries
• glomerular arteries (kidneys)
• vasa nervorum (blood vessels that supply nerves)

Question 2

when does the incidence of microvascular disease increase?

Answer 2

when BP increases

Question 3

what is the mechanism of glucose damage?

Answer 3

hyperglycaemia and hyperlipidaemia cause age-rage, oxidative stress and hypoxia which lead to inflammatory signalling cascades, resulting in local activation of pro-inflammatory cytokines that causes inflammation in the eyes, kidneys and nerves

Question 4

which pathways make glucose damage worse?

Answer 4

• polyol pathway
• AGEs
• Protein Kinase C
• hexosamine

Question 5

what is the main cause of visual loss in people with diabetes and of working age?

Answer 5

diabetic retinopathy

Question 6

what does background diabetic retinopathy involve?

Answer 6

• hard exudates (cheese colour, lipid)
• microaneurysms (“dots”)
• blot haemorrhages

patients have leakage of protein through the vessels

Question 7

what happens to background diabetic retinopathy if diabetes is not controlled and what does this involve?

Answer 7

pre-proliferative diabetic retinopathy resulting in ischaemia of the retina

• soft exudates (cotton wool spots)

Question 8

what happens to to pre-proliferative diabetic retinopathy if it is not treated and what does this involve?

Answer 8

proliferative retinopathy resulting in the formation of new vessels within the retina

• visible, new vessels which can affect vision or bleed (haemorrhage)

Question 9

what is maculopathy?

Answer 9

• specific type of retinopathy which affects colour vision (hard exudates near macula)
• can cause severe visual impairment and threaten direct vision

Question 10

how is diabetic retinopathy managed?

Answer 10

• background DR is managed by improving blood glucose control
• pan retinal photocoagulation can be done to burn off parts of the retina to prevent the change to pre-proliferative and proliferative DR
• laser beams are targeted to parts of the retina undergoing change to prevent vessel formation

Question 11

how is maculopathy managed?

Answer 11

as maculopathy only affects the macula a grid of photocoagulation is done instead of burning the whole retina

Question 12

what is the most common cause of kidney problems?

Answer 12

diabetes

Question 13

what are the histological features of diabetic nephropathy?

Answer 13

• glomerular changes
• vascular changes
• tubulointerstitial changes

Question 14

what glomerular changes occur in diabetic nephropathy?

Answer 14

• mesangial expansion
• basement membrane thickening
• glomerulosclerosis

Question 15

what is the epidemiology of diabetic neuropathy?

Answer 15

• T1DM: 20-40% will have nephropathy after 30-40 years
• T2DM complications occur between 60-70
• racial factors predispose individuals to complications

Question 16

what are the clinical features of diabetic nephropathy?

Answer 16

• progressive proteinuria
• increased BP
• deranged renal function

Question 17

what are the proteinuria ranges?

Answer 17

• normal range: <30mg/24hrs
• microalbuminiruc range: 30-300mg/24hrs
• assymptomatic range: 300-3000mg/24hrs
• nephrotic range: >3000mg/24hr

Question 18

what are the effects of proteinuria?

Answer 18

• hypoalbuminaemia because increased protein loss in urine = less protein in blood
• oedema

Question 19

what are the 4 types of intervention for diabetic nephropathy?

Answer 19

• diabetes control
• BP control
• inhibition of activity of the renin-angiotensin system
• stopping smoking

Question 20

what are the roles of angiotensin 2?

Answer 20

• vasoactive effects
• mediation of glomerular hyperfiltration
• increased tubular uptake of proteins
• induction of pro-fibrotic cytokines
• stimulation of glomerular and tubular growth
• podocyte effects
• upregulation of adhesion molecules on endothelial cells
• upregulation of lipoprotein receptors
• induction of pro-inflammatory cytokines
• stimulates fibroblast proliferation

Question 21

what can an outcome of diabetic neuropathy be?

Answer 21

lower limb amputation

Question 22

what changes are seen in diabetic neuropathy?

Answer 22

• peripheral polyneuropathy
• mononeuropathy (one nerve affected)
• mononeuritis multiplex
• radiculopathy (dermatomes affected)
• autonomic neuropathy
• diabetic amyotrophy (muscle affected)

Question 23

what causes neuropathy?

Answer 23

the blockage of small vessels supplying nerves called vasa nervorum

Question 24

what does peripheral neuropathy involve?

Answer 24

• the longest nerves are affected in the body (those supplying feet)
• this results in a loss of sensation
• more common in tall people
• patients cannot sense an injury to the foot

Question 25

what is the monofilament examination?

Answer 25

the patients feet are exposed and sensation is tested using a monofilament (a metal wire with a set pressure). the monofilament is placed on the bottom of the foot at different positions and the patient is asked if they can feel the sensation

Question 26

what can loss of sensation to the foot result in and how can this be prevented?

Answer 26

multiple fractures because pressure is put on the foot in the wrong way

correct footwear can prevent this

Question 27

what does mononeuropathy involve?

Answer 27

• one part of the nerve doesn’t work (commonly affecting muscles)
• usually sudden motor loss (e.g. foot/wrist drop)
• patients may get cranial nerve palsies (most commonly 3rd nerve palsy -> double vision)

Question 28

what is pupil sparing 3rd nerve palsy?

Answer 28

• eye is usually down and out (as 4th nerve controls downward and 6th nerve controls outward)
• pupil responds to light
• parasympathetic fibres of 3rd cranial nerve does not lose blood supply so pupil is spared

Question 29

what can an aneurysm causing 2rd nerve palsy result in?

Answer 29

parasympathetic fibres are compressed which can cause a fixed dilated pupil (non-pupil sparing)

Question 30

what is mononeuritis multiplex?

Answer 30

a random combination of peripheral nerve lesions

Question 31

what is radiculopathy?

Answer 31

pain over spinal nerves, usually affecting a dermatome on the abdomen or chest wall

Question 32

what is autonomic neuropathy?

Answer 32

loss of sympathetic and parasympathetic nerves to GI tract, bladder and CVS

Question 33

how does autonomic neuropathy present?

Answer 33

GI tract: dysphagia, delayed gastric emptying, constipation/nocturnal diarrhoea, bladder dysfunction

postural hypertension: collapsing on standing

CVS: sudden cardiac death

Question 34

what can normally be detected in a patient with autonomic neuropathy?

Answer 34

a change in heart rate