Microvascular Complications of Diabetes Mellitus

Question 1

State the 3 main sites of microvascular complications.

Answer 1

Retinal arteries (retinopathy) 
Glomerular arterioles (nephropathy) 
Vasa vasorum (neuropathy)

Question 2

What 4 factors correlate with risk of microvascular and macrovascular complications?

Answer 2

Glycaemic control (HbA1c)
Hypertension
Genetics
Glycaemic memory

Question 3

Describe the mechanism of glucose damage to blood vessels.

Answer 3

Hyperglycaemia leads to oxidative stress + hypoxia
This triggers an inflammatory cascade, which leads to local activation of pro-inflammatory cytokines, inflammation + damage

Question 4

What instrument is used to look into the eye?

Answer 4

Fundoscope

Question 5

What are the 4 types of diabetic retinopathy?

Answer 5

Background
Pre-proliferative
Proliferative
Maculopathy

Question 6

What three features do you see in background diabetic retinopathy?

Answer 6

Hard exudates
Microaneurysms
Blot haemorrhages

Question 7

What are hard exudates caused by?

Answer 7

Leakage of lipid contents makes the back of the eye look a cheesy colour

Question 8

Describe pre-proliferative diabetic retinopathy.

Answer 8

Soft exudates (cotton wool spots)  
There will be some haemorrhages

Question 9

What do soft exudates indicate?

Answer 9

Retinal ischaemia

Question 10

Describe proliferative diabetic retinopathy.

Answer 10

Involves the formation of new vessels (in response to retinal ischaemia)
New vessels are generally more fragile + can bleed at any time

Question 11

Describe maculopathy.

Answer 11

Hard exudates near the macula
Same disease as background diabetic retinopathy, but hard exudates are near macula
This can threaten direct vision

Question 12

What are the steps taken in managing background diabetic retinopathy?

Answer 12

Improve blood glucose control

Question 13

What is the treatment for pre-proliferative and proliferative diabetic retinopathy?

Answer 13

Pan-retinal photocoagulation

Question 14

Describe the treatment of maculopathy.

Answer 14

Need a grid of photocoagulation in the affected area (aim to limit damage to the macula (so NOT pan-retinal photo coagulation)

Question 15

State 3 histological features of diabetic nephropathy.

Answer 15

Mesangial expansion
Basement membrane thickening
Glomerulosclerosis (hardening of the capillaries)

Question 16

In diabetic nephropathy you get over production of matrix. What can this be caused by?

Answer 16

Effects of prolonged exposure to high glucose or glycosylated proteins
A rise in pressure within the glomerular capillaries
Angiotensin II

Question 17

State 3 clinical features of diabetic nephropathy.

Answer 17

Progressive proteinuria
Increased BP
Deranged renal function

Question 18

What is the normal range for proteinuria?

Answer 18

< 30 mg/24hr

Question 19

Why do patients with diabetic nephropathy get oedematous?

Answer 19

Increased proteinuria means they are losing albumin through their urine
Decreases serum albumin hence decreases the osmotic potential of the plasma so less fluid is drawn back into the circulation

Question 20

Describe 4 strategies for intervention of patients with diabetic nephropathy.

Answer 20

Improve blood glucose control
BP control
Inhibition of the activity of the RAAS system
Stopping smoking

Question 21

What effect does angiotensin II have on endothelial cells?

Answer 21

It makes endothelial cells more rigid

Question 22

Where is renin produced?

Answer 22

Juxtaglomerular apparatus

Question 23

What can stimulate renin release?

Answer 23

Low renal perfusion (i.e. low BP)

Question 24

Where is ACE found?

Answer 24

Lungs

Question 25

State 3 drug target sites in the renin-angiotensin system.

Answer 25

Drugs blocking renin activity
ACE inhibitors
Angiotensin II receptor blockers (ARBs)

Question 26

What causes diabetic neuropathy?

Answer 26

Occlusion of the vasa vasorum

Question 27

State 6 different types of diabetic neuropathy.

Answer 27

Peripheral polyneuropathy 
Mononeuropathy 
Mononeuritis multiplex 
Radiculopathy 
Autonomic neuropathy 
Diabetic amyotrophy

Question 28

What can peripheral neuropathy lead to, who is it most common in and how can it be tested?

Answer 28

Loss of sensation can lead to damage going unnoticed
Leads to loss of ankle jerks + loss of vibrational sense
Inappropriate use of joints can lead to Charcot joints
Most common in tall people/ those with poor glucose control
Test: monofilament examination

Question 29

What is mononeuropathy?

Answer 29

Usually sudden motor loss e.g. wrist drop or foot drop

Can also cause cranial nerve palsy

Question 30

Why is the pupil spared in pupil sparing third nerve palsy?

Answer 30

Parasympathetic fibres responsible for the diameter of the pupil, run on the outside of the main nerve so they don’t lose their blood supply in diabetes

Question 31

How would an aneurysm causing third nerve palsy present differently to third nerve palsy caused by diabetes?

Answer 31

There would be fixed pupil dilation

Because parasympathetic fibres would also be affected

Question 32

What is mononeuritis multiplex?

Answer 32

A random combination of peripheral nerve lesions

Question 33

What is radiculopathy?

Answer 33

Pain over SPINAL nerves

Usually affecting a dermatome on the abdomen or chest wall

Question 34

What are the effects of autonomic neuropathy on the GI tract?

Answer 34

Difficulty swallowing
Delayed gastric emptying
Constipation/ nocturnal diarrhoea
Bladder dysfunction

Question 35

What are the effects of autonomic neuropathy on the CVS?

Answer 35

Postural hypotension

Sudden cardiac death

Question 36

How can you check for autonomic neuropathy?

Answer 36

Measure changes in heart rate due to Valsalva manoeuvre
Normally there is a change in heart rate
Look at an ECG + compare the R-R intervals

Question 37

What is autonomic neuropathy?

Answer 37

Loss of sympathetic + parasympathetic nerves to GI tract, bladder + cardiovascular system