Laminitis Flashcards
In a horse, there are two sets of Lamellae…
one is sensitive
one is non sensory
[they interlock]
How is the basement membrane on the Lamellae anchored down?
by Hemidesmosomes that are maintained by glucose consuming phosphorylation reactions
What are the three forms of Laminitis?
Sepsis associated
Endocrinopathic
Excessive weight bearing
What diseases cause Sepsis associated laminitis?
Severe GI disease
Pneumonia
Septic Metritis (placenta retention)
How does Sepsis associated laminitis develop from an infection?
Infection causes systemic inflammation which activate cytokine expression > this causes oxidative injury in the desmosomes
What are the three most common causes of Endocrinopathic Lamnitis?
Equine Metabolic Syndrome (EMS)
Pituitary Pars Intermedia Disorder (PPID)
Glucocorticoid usage
Endocrinopathic Laminitis and its causes are strongly associated with what mechanics? (4)
Hyperinsulinaemia
Inappropriate IGF-1R stimulation (insulin growth factor)
Altered adipokines (agonise the function of insulin)
Altered proteostasis (cell function)
How can we differentiate Endocrinopathic and Sepsis Laminitis on Histology?
Endo- lamellae appears stretched and elongated with some mitotic figures present
Sepsis- lamellae layers are seperated
How does EMS alter normal body metabolism? (3)
Causes excessive insulin response to oral carbohydrates
Increases fasting
Alters the adipokines
What may cause insulin dysregulation in EMS? (4)
Genetics, Obesity, Diet, Endocrine disrupting chemicals e.g. pesticides, fertilizers
How does PPID cause laminitis?
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
How do excessive Corticosteroids cause Laminitis?
Cortisol antagonises insulin leading to hyper production and therefore hyperinsulinaemia
What is the least common type of Laminitis and how does this develop?
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
What are the three stages of Laminitis development?
Developmental- contact with trigger
Acute laminitis- clinical signs
Chronic laminitis- pedal bone movement or remodelling
How do we diagnose Laminitis on the physical exam?
Lameness &/or characteristic stance- leaning/ positioned on their heel
Bounding digital pulses
Increased hoof wall temperature
Palpable depression at the coronary band
When would we use radiography in Laminitis cases?
If concerned that P3 has moved (softening of the sole or depression at coronary band)
How do we take a radiograph of a Laminitic patient?
Lateromedial
with markers on the dorsal hoof wall to assess the angle of the bone
How do we test for PPID?
What is important to remember to do for this?
Basal ACTH- remember to use seasonally adjusted reference ranges- horses are seasonal breeders!
Can also do a TRH stimulation test
When is a TRH stimulation test indicated and how does it work?
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
When can’t we perform a TRH stimulation test?
Autumn- there’s no reference ranges for it
We can diagnose EMS using any insulin dysregulation test…
When is this contraindicated?
Contraindicated in horses with active laminitis- as will have elevated cortisol in the blood which would give a false positive
What is the best method to diagnosing EMS?
Oral glucose or oral sugar test- measure insulin increase
What NSAID is best recommended for Laminitis patients?
Phenylbutazone, Flunixin
I/V or oral
When would we suggest digital cryotherapy to treat Laminitis?
Only for sepsis associated laminitis
How do we further manage Laminitis non medically?
Box rest
Alter diet- no grass, use chopped up fibre such as unmollassed beet, and give poor quality hay
How is PPID treated?
Pergolide- dopamine receptor agonist
What is the main priority when preventing Endocrinopathic Laminitis?
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
