Laminitis Flashcards
what is laminitis
degeneration then failure of interdigitation between P3 and inside of hoof wall —> breakdown and separation
How are laminae made up
Dermal lamellae (P3) and epidermal lamellae (hoof) are strongly bonded
Name 2 endocrine cause of laminitis
obesity/ equine metabolic syndrome
Pars Pituitary intermedia dysfunction (PPID)
what occurs in equine metabolic syndrome
Increased bodily fat reduces the cellular response to insulin – insulin resistance / dysregulation
This causes more insulin to be released
excess insulin in blood stream stimulates excess MMP production increasing risk of laminitis
how does increased insulin lead to increased MMP production
not understood
How does PPID lead to laminitis
Excess Adrenocorticotrophic hormone (ACTH) also causes hyperinsulinaemia
stimulates excess MMP production increasing the risk of laminitis
List some non-endocrine causes of laminitis
toxic - compromised bowel or sever infection
support limb laminitis
corticosteroid induced
stress
Describe how severe infections lead to laminitis
Bacterial endotoxin enters the blood stream – endotoxaemia
MMP production is increased
Describe support limb laminitis
Severe lameness in 1 limb causes excessive weight bearing in contra-lateral limb–> reduces blood flow to laminae causing hypoxia –> inflammation and MMP production
therefore support limb laminitis is often unilateral
Describe the importance of MMP in laminitis
MMP are catabolic enzymes
they release the bond between dermal lamella (P3) and epidermal lamellae (hoof)
how can corticosteroids administration lead to laminitis
exogenous glucocorticoids
Induce hyperinsulinaemia and subsequent increase MMP production as above
Risk greater in animals that are already susceptible
describe how stress can lead to laminitis
endogenous glucocorticoids increase- due to fight/ flight situation
Induce hyperinsulinaemia and subsequent increase MMP production as above
Risk greater in animals that are already susceptible
describe the signalment of laminitis
age- no consistent predisposition
breed- occurs in all breeds of horse but native breeds/ ponies predisposed
sex- no predisposition
when is the peak incidence of equine laminitis
spring and autumn
linked to grass growth
but can occur all year round
what signs in the horses stance suggest laminitis
leaning backwards
weight shifting
List 4 signs of PPID
hirsuitism- long curly winter coat
decreased muscle mass
‘pot belly’ appearance
supra orbital fat pads become more evident
List 2 signs of EMS
excess body condition
abnormal fat distribution
which limbs does laminitis generally affect
often affects both front limbs
May be all 4 limbs, just 1 limb or just the hind limbs
List 2 signs of laminitis in the foot
increased digital pulse
hooves warm to touch
what on the foot can suggest severe laminitic disease
Depression at coronary band and loss of concavity of sole (sinking of the pedal bone )
what do you look for on limb specific exam in laminitis cases
Visible growth rings indicate previous episodes
Able to lift legs
often show pain to hoof testers at point of frog
Depression at coronary band and loss of concavity of sole suggest severe disease (sinking)
describe what we see on dynamic exam with laminitis
Degree of lameness varies
Usually worse when turning and on hard ground
Foot lands heel first to spare the toe region from weight bearing
Sometimes show a high stepping gait with hind limb laminitis.
what 2 radiographs are taken when investigating laminitis
latero-medial view
dorso-palmar view
describe the limits for rotation of the pedal bone on radiography in laminitis
<5 mild
5-10 moderate
>10 severe
List the 2 ways to test for EMS
baseline insulin (serum)
oral sugar challenge test
describe the baseline insulin (serum ) test
Feed only hay / grass for 12 hours prior
Positive result (increased baseline insulin) is diagnostic for EMS
Negative result (normal baseline insulin) does not rule the disease out – lots of false negatives
Describe the oral sugar challenge test
Feed only hay / grass for 12 hours prior
Feed Karo light corn syrup or dextrose powder
Blood sample for insulin 60-90 mins later
List the 2 ways to test for PPID
Baseline ACTH (EDTA)- usually diagnostic
Thyrotropin Releasing Hormone stimulation test
Describe the baseline ACTH test
Usually diagnostic
Reference range changes through the year
Usually most accurate in the autumn
Describe the Thyrotropin Releasing Hormone stimulation test
Rarely required because baseline ACTH test usually diagnostic for PPID
Collect baseline ACTH
Inject TRH
Collect another ACTH 10 minutes later
what do you need to consider when testing for EMS and PPID
Results are inaccurate if animal is in pain – maybe wait a few days until more comfortable (after given pain relief)
Describe the initial management of laminitis
pain relief -NSAIDs (phenylbutazone), paracetamol, opiates
Vasodilator
support feet
what/why vasodilators are used in laminitis cases
Improve blood supply to distal limbs
Acepromazine
describe how to support feet in laminitis cases
confine to stable on deep shaving beds
remove shoes
use frog supports
Describe diet changes in cases of laminitis
1.5-2% body weight dry weight hay, soaked for 1 hour to reduce sugar content
Tiny amount of low sugar food (alfalfa) to put medication in
Vitamin / mineral balancer
List 3 drugs that can treat EMS
metformin, levothyroxine, ertugliflozin
List 2 drugs that can be used to treat PPID
pergolide, cabergoline
what can farriers do to support horses with laminitis
trim heels and toes
heart bar shoes
what is a salvage procedure in laminitis
deep digital flexor tenotomy
used if we can’t stop the rotation of the P3
this removes the palmar traction on P3
salvage only
List 5 factors that affect prognosis of lainitis
lameness severity
Degree of rotation
Sinking
Patient weight
Ability to control endocrine disease
Describe how laminits occurs
dermal lamellae and epidermal lamella are strongly bonded - to allow the hoof to grow, MMPs release the bonds and allow the lamina to slide, laminitis occurs due to degradation of the interdigitation - often a result of excess MMP activity
