Laminitis

Question 1

In a horse, there are two sets of Lamellae…

Answer 1

one is sensitive
one is non sensory

[they interlock]

Question 2

How is the basement membrane on the Lamellae anchored down?

Answer 2

by Hemidesmosomes that are maintained by glucose consuming phosphorylation reactions

Question 3

What are the three forms of Laminitis?

Answer 3

Sepsis associated
Endocrinopathic
Excessive weight bearing

Question 4

What diseases cause Sepsis associated laminitis?

Answer 4

Severe GI disease
Pneumonia
Septic Metritis (placenta retention)

Question 5

How does Sepsis associated laminitis develop from an infection?

Answer 5

Infection causes systemic inflammation which activate cytokine expression > this causes oxidative injury in the desmosomes

Question 6

What are the three most common causes of Endocrinopathic Lamnitis?

Answer 6

Equine Metabolic Syndrome (EMS)
Pituitary Pars Intermedia Disorder (PPID)
Glucocorticoid usage

Question 7

Endocrinopathic Laminitis and its causes are strongly associated with what mechanics? (4)

Answer 7

Hyperinsulinaemia
Inappropriate IGF-1R stimulation (insulin growth factor)
Altered adipokines (agonise the function of insulin)
Altered proteostasis (cell function)

Question 8

How can we differentiate Endocrinopathic and Sepsis Laminitis on Histology?

Answer 8

Endo- lamellae appears stretched and elongated with some mitotic figures present
Sepsis- lamellae layers are seperated

Question 9

How does EMS alter normal body metabolism? (3)

Answer 9

Causes excessive insulin response to oral carbohydrates
Increases fasting
Alters the adipokines

Question 10

What may cause insulin dysregulation in EMS? (4)

Answer 10

Genetics, Obesity, Diet, Endocrine disrupting chemicals e.g. pesticides, fertilizers

Question 11

How does PPID cause laminitis?

Answer 11

In PPID there’s a loss of dopaminergic inhibition leading to an excessive production of pituitary hormones such as cortisol which cause hyperinsulinemia leading to Laminitis

Question 12

How do excessive Corticosteroids cause Laminitis?

Answer 12

Cortisol antagonises insulin leading to hyper production and therefore hyperinsulinaemia

Question 13

What is the least common type of Laminitis and how does this develop?

Answer 13

Supporting Limb Laminitis- injury causes horse to place weight on opposing limb leading to inadequate perfusion in the injured limb > causes hypoxic lamellae causing them to separate

Question 14

What are the three stages of Laminitis development?

Answer 14

Developmental- contact with trigger
Acute laminitis- clinical signs
Chronic laminitis- pedal bone movement or remodelling

Question 15

How do we diagnose Laminitis on the physical exam?

Answer 15

Lameness &/or characteristic stance- leaning/ positioned on their heel
Bounding digital pulses
Increased hoof wall temperature
Palpable depression at the coronary band

Question 16

When would we use radiography in Laminitis cases?

Answer 16

If concerned that P3 has moved (softening of the sole or depression at coronary band)

Question 17

How do we take a radiograph of a Laminitic patient?

Answer 17

Lateromedial
with markers on the dorsal hoof wall to assess the angle of the bone

Question 18

How do we test for PPID?
What is important to remember to do for this?

Answer 18

Basal ACTH- remember to use seasonally adjusted reference ranges- horses are seasonal breeders!
Can also do a TRH stimulation test

Question 19

When is a TRH stimulation test indicated and how does it work?

Answer 19

Used when ACTH test is inconclusive
TRH is a releasing factor so causes release of all pituitary hormones- then ACTH levels are measured in response to that

Question 20

When can’t we perform a TRH stimulation test?

Answer 20

Autumn- there’s no reference ranges for it

Question 21

We can diagnose EMS using any insulin dysregulation test…
When is this contraindicated?

Answer 21

Contraindicated in horses with active laminitis- as will have elevated cortisol in the blood which would give a false positive

Question 22

What is the best method to diagnosing EMS?

Answer 22

Oral glucose or oral sugar test- measure insulin increase

Question 23

What NSAID is best recommended for Laminitis patients?

Answer 23

Phenylbutazone, Flunixin
I/V or oral

Question 24

When would we suggest digital cryotherapy to treat Laminitis?

Answer 24

Only for sepsis associated laminitis

Question 25

How do we further manage Laminitis non medically?

Answer 25

Box rest
Alter diet- no grass, use chopped up fibre such as unmollassed beet, and give poor quality hay

Question 26

How is PPID treated?

Answer 26

Pergolide- dopamine receptor agonist

Question 27

What is the main priority when preventing Endocrinopathic Laminitis?

Answer 27

Minimise consumption of NSC- the energy in growing plants
it decreases when plant is growing and increases when the plant is photosynthesising in low temperatures, high light intensity or low water
so avoid grazing when it is high