PBL 7: Complication of Diabetes

Question 1

What structures make up the glomerulus?

Answer 1

Bowman’s capsule:

• fenestrated capillary endothelium
• podocytes with pedicel diaphragm slit
• basement membrane containing proteoglycans/collagen/water

Question 2

What is the function of the glomerulus?

Answer 2

High pressure selective filtration

Question 3

What structures can and cannot cross the glomerulus and why?

Answer 3

• small and positively charged molecules can (water, urea, glucose, electrolytes, creatinine, amino acids)
• negative solutes cannot as get repelled by the basement membrane and capillary endothelium which are both negative
• larger molecules cannot as do not fit through small capillary fenestrations and podocyte slits
• large plasma proteins and RBCs are negative and large so cannot pass through

Question 4

What is the significance of albuminuria?

Answer 4

On podocyte injury albumin can enter the filtrate

Podocyte foot processes fall off/detach/apoptosis occurs

Question 5

What is the difference between microalbuminuria and proteinuria?

Answer 5

Microalbuminuria - 30-300 ACR (albumin creatinine ratio)

Proteinuria - >300 ACR so ongoing damage

Question 6

What is ACR?

Answer 6

Albumin creatinine ratio
Amount excreted in 24 hours
should be <30mg

Question 7

How is glucose reabsorbed by the kidney?

Answer 7

• Basal Na+/K+ ATPase transporter secretes Na+ into the blood maintain a low IC Na+ concentration
• Apical Na+/glucose co-transporter transporters glucose and sodium into the tubular cell down chemical gradient created

Question 8

What is eGFR?

Answer 8

measure serum creatinine - if low GFR serum creatinine should be high

Question 9

What is MDRD?

Answer 9

Takes into account creatinine levels of individual, age, gender and ethnicity when measuring GFR

Question 10

What are the effects of high glucose on the kidney?

Answer 10

• glomerulosclerosis: scarring of glomerulus
• thickened basement membrane
• glycosylation of the basement membrane
• podocyte apoptosis
• vasodilation of afferent arteriole = greater filtration pressure = capillary damage = mesangial cell damage, podocyte apoptosis, glomerular sclerosis
• saturated glucose transporters so glucose cannot all be reabsorbed and ends up in urine = glucosuria = osmotic diuresis = polyuria

Question 11

What are the types of neuropathy that can occur due to diabetes?

Answer 11

• peripheral (hands and feet pain and loss of sensation)
• focal (affect one nerve in the body)
• autonomic (autonomic branches affected - digestion/bowel/bladder control)
• proximal (pain in thigh and hips)

Question 12

How does diabetic retinopathy occur?

Answer 12

• micro blood-vessels damaged = microvascular disease

Question 13

What may you see in non-proliferative diabetic retinopathy?

Answer 13

Damaged vessel leaks:

increase in fluid, blood, cholesterol deposits, cotton wool spots, nerve fibre damage

Question 14

What may you see in proliferative diabetic retinopathy?

Answer 14

New vessels angiogenesis/neovascularisation

Fragile vessels = burst = blur vision

Question 15

How do you examine diabetic retinopathy?

Answer 15

Ophthalmoscopy/fundoscopy

examine ocular fundus and assess retinal manifestations of hypertension/retinal detachment/macular degeneration/melanoma