Endo 17 - Microvascular complications of DM

Question 1

Where are the sites of microvascular complications?

Answer 1

Retinal arteries, glomerular arterioles (kidney), vasa nervorum (tiny blood vessels supplying nerves)

Question 2

What do microvascular complications depend on?

Answer 2

1. Severity of hyperglycaemia
2. Hypertension
3. Genetics
4. “Hyperglycaemic memory” - initial years very important in preventing microvascular complications, and poor initial control cannot be mitigated by good present control
5. Tissue damage (originally reversible, later irreversible - via alterations in proteins)

Question 3

What are the mechanisms of glucose damage

Answer 3

1. Polyol pathway
2. AGEs
3. Protein Kinase C
4. Hexosamine

Question 4

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

Answer 4

Diabetic retinopathy

Question 5

In a normal retina, the optic disc is bright and the fovea/macula is the dark spot. In background diabetic retinopathy, what are the features

Answer 5

Background diabetic retinopathy:

1. Hard exudates (cheese colour)
2. Microaneurysms
3. Blot haemorrhages

Question 6

If background diabetic retinopathy isn’t treated, what happens?

What is a feature of this stage of diabetic retinopathy?

Answer 6

We get pre-proliferative diabetic retinopathy

1. We get soft exudates - cotton wool spots (showing retinal ischaemia)

Question 7

If pre-proliferative retinopathy isn’t treated, we can get proliferative retinopathy. What are features of this

Answer 7

1. Visible new vessels - chaotic and unsmooth

2. New vessels may affect vision directly or bleed - causing visual loss

Question 8

Describe maculopathy

Answer 8

Variant of diabetic retinopathy

Hard exudates near macula - can threaten direct vision

Question 9

How is background diabetic retinopathy managed

Answer 9

Improve blood glucose control - warn patients that warning signs are present

Question 10

How are pre-proliferative and proliferative diabetic retinopathy managed?

Answer 10

Pre-proliferative (cotton wool spots)= Suggests general ischaemia (if left untreated, new vessels will grow). Requires pan retinal photocoagulation - laser burns pre-proliferative parts of retina before new vessels grow

Proliferative diabetic retinopathy (visible new vessels) = requires pan retinal photocoagulation

Question 11

Describe treatment/management of maculopathy

Answer 11

Grid-focused retinal photocoagulation

Question 12

What can diabetic nephropathy result in

Answer 12

1. Hypertension
2. Proteinuria (progressively increasing)
3. Progressively deteriorating kidney function
4. Classic histological features

Question 13

What are the histological features of diabetic nephropathy

Answer 13

Glomerular changes:

1. Mesangial expansion
2. Basement membrane thickening
3. Glomerulosclerosis

Vascular changes
Tubulointerstitial changes

Question 14

What are the strategies for intervention of diabetic nephropathy

Answer 14

1. Diabetic control - decreasing HbA1c reduces microvascular complication risk
2. BP control - BP rise = decline in kidney function and GFR
3. Inhibition of RAS - via ACEi
4. Stopping smoking

Question 15

What is the most common cause of neuropathy and subsequent lower limb amputation?

Answer 15

Diabetic neuropathy

Occurs when small vessels supplying nerves (vasa nervorum) are blocked

Question 16

Peripheral neuropathy is more likely to occur in?

Answer 16

Tall patients, patients with poor glucose control

Question 17

Describe peripheral neuropathy - clinical signs

Answer 17

1. Loss of ankle jerk
2. Loss of vibration sense (use tuning fork)
3. Multiple fractures on foot X-ray

Question 18

Describe mononeuropathy

Answer 18

Affect 1 nerve - commonly motor nerves affected - can cause foot/wrist drop

Or CN palsy - e.g. double vision / CN3 palsy

Question 19

Diabetes causes what type of 3rd nerve palsy

Answer 19

Pupil sparing - i.e. no dilation

If dilation - then tumour or something

Question 20

Describe mononeuritis multiplex

Answer 20

Random combination of peripheral nerve lesions

Question 21

Describe radiculopathy

Answer 21

Pain over spinal nerves, usually affects dermatome on abdomen or chest wall

Question 22

Describe autonomic neuropathy

Answer 22

Loss of SNS and PNS to GIT, bladder, CVS

Difficulty swallowing, delayed gastric emptying, constipation, bladder dysfunction, postural hypotension

Question 23

What are the tests that can be done for autonomic neuropathy

Answer 23

Measure changes in HR in response to valsalva manoeuvre

Usually change in HR - look at ECG and compare R-R interval