Microvascular Complications of Diabetes Mellitus

Question 1

State the three main sites of microvascular complications.

Answer 1

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

Question 2

What factors correlate with risk of microvascular and macrovascular complications?

Answer 2

Glycaemic control (HbA1c)
Hypertension
Other factors such as glycaemic memory and genetics can contribute

Question 3

Describe the mechanism of glucose damage to blood vessels.

Answer 3

Hyperglycaemia leads to oxidative stress and hypoxia

This triggers an inflammatory cascade, which leads to damage

Question 4

What instrument is used to look into the eye?

Answer 4

Fundoscope

Question 5

Where is the optic disc relative to the macula on the back of the eye?

Answer 5

The optic disc is nasal to the macula

Question 6

What are the 4 types of diabetic retinopathy?

Answer 6

Background
Pre-proliferative
Proliferative
Maculopathy

Question 7

What three features do you see in background diabetic retinopathy?

Answer 7

Hard exudates
Microaneurysms
Blot haemorrhages

Question 8

What are hard exudates caused by?

Answer 8

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

Question 9

Describe pre-proliferative diabetic retinopathy.

Answer 9

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

Question 10

What do soft exudates indicate?

Answer 10

Retinal ischaemia

Question 11

Describe proliferative diabetic retinopathy.

Answer 11

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

Question 12

Describe maculopathy.

Answer 12

Presence of hard exudates in the macula
This is the same disease as background diabetic retinopathy, it’s just that the hard exudates are in the macula
This can threaten direct vision

Question 13

What are the steps taken in managing background diabetic retinopathy?

Answer 13

Improve blood glucose control

Question 14

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

Answer 14

Pan-retinal photocoagulation

Question 15

Describe the treatment of maculopathy.

Answer 15

You need a grid of photocoagulation in the affected area (aim to limit damage to the macula so you don’t do pan-retinal photo coagulation)

Question 16

State some histological features of diabetic nephropathy.

Answer 16

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

Question 17

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

Answer 17

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

Question 18

State 3 clinical features of diabetic nephropathy.

Answer 18

Progressive proteinuria
Increased blood pressure
Deranged renal function

Question 19

What is the normal range for proteinuria?

Answer 19

< 30 mg/24hr

Question 20

Why do patients with diabetic nephropathy get oedematous?

Answer 20

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

Question 21

Describe some strategies for intervention of patients with diabetic nephropathy.

Answer 21

Improve blood glucose control
Blood pressure control
Inhibition of the activity of the renin-angiotensin system
Stopping smoking

Question 22

What effect does angiotensin II have on endothelial cells?

Answer 22

It makes endothelial cells more rigid

Question 23

Where is renin produced?

Answer 23

Juxtaglomerular apparatus

Question 24

What can stimulate renin release?

Answer 24

Low renal perfusion (i.e. low blood pressure)

Question 25

Where is ACE found?

Answer 25

Lungs

Question 26

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

Answer 26

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

Question 27

What causes diabetic neuropathy?

Answer 27

Occlusion of the vasa vasorum

Question 28

State 6 different types of diabetic neuropathy.

Answer 28

``` Peripheral polyneuropathy Mononeuropathy Mononeuritis multiplex Radiculopathy Autonomic neuropathy Diabetic amyotrophy ```

Question 29

What can peripheral neuropathy lead to and how can it be tested?

Answer 29

Loss of sensation can lead to damage going unnoticed It also leads to loss of ankle jerks and loss of vibrational sense Inappropriate use of joints can lead to Charcot joints Test – monofilament examination

Question 30

What is mononeuropathy?

Answer 30

Usually sudden motor loss e.g. wrist drop or foot drop | Can also cause cranial nerve palsy

Question 31

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

Answer 31

The parasympathetic fibres, that are 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 32

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

Answer 32

There would be fixed pupil dilation | This is because the parasympathetic fibres would also be affected

Question 33

What is mononeuritis multiplex?

Answer 33

A random combination of peripheral nerve lesions

Question 34

What is radiculopathy?

Answer 34

Pain over SPINAL nerves | Usually affecting a dermatome on the abdomen or chest wall

Question 35

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

Answer 35

Difficulty swallowing Delayed gastric emptying Constipation/nocturnal diarrhoea NOTE: it can also lead to bladder dysfunction

Question 36

What are the effects of autonomic neuropathy on the CVS?

Answer 36

Postural hypotension | There have been reports of sudden cardiac death

Question 37

How can you check for autonomic neuropathy?

Answer 37

Measure changes in heart rate due to Valsalva manoeuvre | Look at an ECG and compare the R-R intervals