17. Microvascular complications Flashcards
what are the common sites of microvascular complication?
- retinal arteries
- glomerular arteries (kidneys)
- vasa nervorum (blood vessels that supply nerves)
when does the incidence of microvascular disease increase?
when BP increases
what is the mechanism of glucose damage?
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
which pathways make glucose damage worse?
- polyol pathway
- AGEs
- Protein Kinase C
- hexosamine
what is the main cause of visual loss in people with diabetes and of working age?
diabetic retinopathy
what does background diabetic retinopathy involve?
- hard exudates (cheese colour, lipid)
- microaneurysms (“dots”)
- blot haemorrhages
patients have leakage of protein through the vessels
what happens to background diabetic retinopathy if diabetes is not controlled and what does this involve?
pre-proliferative diabetic retinopathy resulting in ischaemia of the retina
- soft exudates (cotton wool spots)
what happens to to pre-proliferative diabetic retinopathy if it is not treated and what does this involve?
proliferative retinopathy resulting in the formation of new vessels within the retina
- visible, new vessels which can affect vision or bleed (haemorrhage)
what is maculopathy?
- specific type of retinopathy which affects colour vision (hard exudates near macula)
- can cause severe visual impairment and threaten direct vision
how is diabetic retinopathy managed?
- 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
how is maculopathy managed?
as maculopathy only affects the macula a grid of photocoagulation is done instead of burning the whole retina
what is the most common cause of kidney problems?
diabetes
what are the histological features of diabetic nephropathy?
- glomerular changes
- vascular changes
- tubulointerstitial changes
what glomerular changes occur in diabetic nephropathy?
- mesangial expansion
- basement membrane thickening
- glomerulosclerosis
what is the epidemiology of diabetic neuropathy?
- T1DM: 20-40% will have nephropathy after 30-40 years
- T2DM complications occur between 60-70
- racial factors predispose individuals to complications
what are the clinical features of diabetic nephropathy?
- progressive proteinuria
- increased BP
- deranged renal function
what are the proteinuria ranges?
- normal range: <30mg/24hrs
- microalbuminiruc range: 30-300mg/24hrs
- assymptomatic range: 300-3000mg/24hrs
- nephrotic range: >3000mg/24hr
what are the effects of proteinuria?
- hypoalbuminaemia because increased protein loss in urine = less protein in blood
- oedema
what are the 4 types of intervention for diabetic nephropathy?
- diabetes control
- BP control
- inhibition of activity of the renin-angiotensin system
- stopping smoking
what are the roles of angiotensin 2?
- 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
what can an outcome of diabetic neuropathy be?
lower limb amputation
what changes are seen in diabetic neuropathy?
- peripheral polyneuropathy
- mononeuropathy (one nerve affected)
- mononeuritis multiplex
- radiculopathy (dermatomes affected)
- autonomic neuropathy
- diabetic amyotrophy (muscle affected)
what causes neuropathy?
the blockage of small vessels supplying nerves called vasa nervorum
what does peripheral neuropathy involve?
- 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
what is the monofilament examination?
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
what can loss of sensation to the foot result in and how can this be prevented?
multiple fractures because pressure is put on the foot in the wrong way
correct footwear can prevent this
what does mononeuropathy involve?
- 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)
what is pupil sparing 3rd nerve palsy?
- 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
what can an aneurysm causing 2rd nerve palsy result in?
parasympathetic fibres are compressed which can cause a fixed dilated pupil (non-pupil sparing)
what is mononeuritis multiplex?
a random combination of peripheral nerve lesions
what is radiculopathy?
pain over spinal nerves, usually affecting a dermatome on the abdomen or chest wall
what is autonomic neuropathy?
loss of sympathetic and parasympathetic nerves to GI tract, bladder and CVS
how does autonomic neuropathy present?
GI tract: dysphagia, delayed gastric emptying, constipation/nocturnal diarrhoea, bladder dysfunction
postural hypertension: collapsing on standing
CVS: sudden cardiac death
what can normally be detected in a patient with autonomic neuropathy?
a change in heart rate
