PATHOLOGY - Equine Endocrine Disease and Laminitis Flashcards

1
Q

What is laminitis?

A

Laminitis is inflammation and/or fluid accumulation between the dermal and epidermal lamellae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe the blood supply to the laminae

A

The laminae are supplied by the laminar arteries which branch from the circumflex arteries and are drained by the laminar veins which drain into the circumflex veins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why are the digital veins so sensitive to vasoactive mediators?

A

The digital veins are highly muscular are are thus very sensitive to vasoactive mediators

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the three classifications of laminitis?

A

Hyperinsulinaemia-associated laminitis (HAL)
Sepsis associated laminitis
Supporting limb laminitis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the four possible triggers of laminitis?

A

Activation/infiltration of white blood cells
Increased pro-inflammatory mediators
Decreased anti-inflammatory mediators
Increased COX-2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the two main theories of laminitis?

A

Vascular theory
Enzymatic theory

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What does the vascular theory propose as the triggering factors of laminitis?

A

Endothelial cell dysfunction
Release of vasoactive mediators

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

List three possible causes of endothelial cell dysfunction resulting in laminitis?

A

Insulin resistance
Hyperglycaemia
Hyperinsulinaemia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How does endothelial cell dysfunction and/or vasoactive mediator release trigger laminitis according to the vascular theory?

A

Endothelial cell dysfunction and vasoactive mediators cause a disruption in blood flow to the laminae resulting in vasoconstriction which results in an increase in fluid movement from the vessels into the interstitial space causing an increase in interstitial hydrostatic pressure and oedema between the laminae. This results in the formation of arteriovenous shunts between the circumflex vessels, causing blood to bypass the laminae resulting in ischaemia, inflammation and necrosis causing seperation of the dermal and epidermal laminae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does the enzymatic theory propose as the triggering factors of laminitis?

A

Increased matrix metalloproteinase (MMP) activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the normal function of matrix metalloproteinases (MMPs) in the hoof?

A

Normally, matrix metalloproteinases are involved in normal growth of the hoof through enabling the epidermal laminae to glide past the dermal laminae to allow for hoof growth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How does increased matrix metalloproteinase (MMP) activity trigger laminitis according to the enzymatic theory?

A

Increase matrix metalloproteinase (MMP) activity can result in the break down of the extracellular matrix (ECM) and basement membranes which form the junction between the dermal and epidermal laminae, resulting in laminae seperation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe how insulin resistance can contribute to laminitis

A

Insulin resistance reduces glucose uptake by the laminae which causes seperation of the dermal and epidermal laminae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe how hyperglycaemia can contribite to laminitis

A

Hyperglycaemia causes increased insulin secretion and as insulin is a pro-inflammatory mediator this causes endothelial cell dysfunction and vasoconstriction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What can occur following seperation of the dermal and epidermal lamellae?

A

Pedal bone rotation and possible pedal bone sinking

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe the phases of laminitis

A
  1. Trigger factors +/- predisposing factors
  2. Developmental phase which lasts several hours
  3. Acute phase which lasts for several days and presents with pain and lameness
  4. The acute phase can lead to either the subacute or chronic phase. The subacute phase is classified as there is no pedal bone collapse however the clinical signs have persisted beyond 72 hours. The chronic phase is classified as lamellar seperation and pedal bone collapse
17
Q

What are the three main clinical signs of laminitis?

A

Pain
Strong digital pulses
Abnormal hoof morphology

18
Q

How can you tell if a horse is in pain due to laminitis?

A

Rocking back and forth
Shortened strides
Reluctant to turn
Reluctant to move at all
Reluctant to have feed picked up
Pain with hoof testers on their toes

19
Q

Describe the abnormal hoof morphologies that can be indicative of laminitis?

A

Long toe
Long heel
Laminitic rings
Flattened or concave sole due to pedal bone collapse

20
Q

How would you describe a horse with a laminitis score of 1 using the Obel grading scale?

A

Horse is frequently lifting their feet (i.e. not putting as much weight on each foot)

21
Q

How would you describe a horse with a laminitis score of 2 using the Obel grading scale?

A

Horse is willing to walk and can lift forefeet without difficulty however does have a laminitic gait

22
Q

How would you describe a horse with a laminitis score of 3 using the Obel grading scale?

A

Horse resists lifting forefoot and moves reluctantly

23
Q

How would you describe a horse with a laminitis score of 4 using the Obel grading scale?

A

Horse is forced to move and may or may not be recumbent

24
Q

How should laminitis be treated?

A

It is important to treat the underlying cause of laminitis in combination with box rest, hoof support and analgesia

25
Q

What are the two main metabolic syndromes that can predispose horses to laminitis?

A

Equine metabolic syndrome (EMS)
Pituitary pars intermedia dysfunction (PPID)

26
Q

What are the three primary criteria required to diagnose equine metabolic syndrome (EMS)?

A

Obesity
Insulin dysregulation
Predispostion to laminitis

27
Q

Which two diagnostic tests can be carried out for equine metabolic syndrome (EMS)?

A

Oral sugar test
Combined glucose-insulin test (CGIT)

28
Q

Describe how to carry out an oral sugar test for equine metabolic syndrome (EMS)?

A
  1. Fast the horse for 3 - 6 hours
  2. Administer 0.45ml\kg of corn syrup
  3. Measure insulin levels in the blood at 0 (basal), 60 and/or 90 minutes to look for excess insulin in the blood
29
Q

Describe how to carry out a combined glucose-insulin test (CGIT) for equine metabolic syndrome (EMS)?

A
  1. Fast horse for 6 hours and place an I.V. catheter
  2. Take basal blood insulin and glucose levels
  3. Administer 150mg/kg 50% dextrose sugar I.V. and 0.1 U/kg of insulin I.V.
  4. Measure blood glucose levels at regular intervals
  5. Measure blood insulin levels at 45 minutes
  6. There is insulin resistance if glucose levels remain above baseline for 45 minutes or more
30
Q

What should be done to treat equine metabolic syndrome (EMS)?

A

Weight loss

31
Q

What can be done to promote weight loss in horses?

A

Don’t turn out onto pasture
Feed hay only
Increase exercise

32
Q

Why should hay be soaked for at least 60 minutes when promoting weight loss in a horse with equine metabolic syndrome (EMS)?

A

Soaking the hay removes any non-structural carbohydrates

33
Q

Which two diagnostic tests can you carry out for pituitary pars intermedia dysfunction (PPID) ?

A

Basal ACTH concentration
TRH stimulation test

34
Q

When would you carry out a basal ACTH concentration test?

A

If you are presented with an older horse with obvious clinical signs of pituitary pars intermedia dysfunction (PPID)

35
Q

When would you carry out a TRH stimulation test?

A

If you are presented with a young horse with mild clinical signs or if you have ended up with an equivocal basal ACTH concentration test

36
Q

How should you treat pituitary pars intermedia dysfunction (PPID)?

A

Administration of a dopamine agonist