PATHOLOGY - Laminitis Flashcards
What is laminitis?
Laminitis is inflammation and/or fluid accumulation between the dermal and epidermal lamellae
Which factors can trigger laminitis?
Endotoxaemia
Systemic inflammatory response
Hormonal imbalances
Mechanical overload
Dietary factors
List some examples of causes of endotoxaemia which can result in laminitis
Grain overload
Colitis
Infection
List some examples of causes of a systemic inflammatory response which can result in laminitis
Trauma
Infection
Severe stress
List some causes of hormonal imbalances which can result in laminitis
Equine metabolic syndrome (EMS) resulting in insulin dysregulation
Equine pars intermedia dysfunction (PPID) which results in secondary insulin resistance
Which dietary factors can result in laminitis?
Increased non-structural carbohydrates can result in laminitis
What is the proposed pathophysiology of laminitis?
Following the triggering event ± the influence of predisposing factors for laminitis, one of the early mechanisms in laminitis is vasoconstriction within the lamellae which can result in altered blood flow, ischaemia and hypoxia. This usually occurs in response to inflammatory mediators. Inflammation, endotoxaemia and decreased glucose uptake can all result in increased activation of matrix metalloproteinases (MMPs) which will break down the extracellular matrix (ECM) and basement membrane which forms the junction between the dermal and epidermal lamellae, resulting in lamellar separation
What can occur following seperation of the dermal and epidermal lamellae?
Separation of the dermal and epidermal lamellae can result in pedal bone rotation and sinking
What are the phases of laminitis?
- Triggering factors ± predisposing factors to laminitis
- Developmental phase which lasts 20 to 60 hours
- Acute phase which lasts 1 to 3 days and presents with clinical signs of pain and acute laminitis
- The acute phase can either progress to the subacute phase or the chronic phase. The subacute phase is where there is no pedal bone collapse however the clinical signs have persisted beyond 72 hours. The subacute phase can progress to the chronic phase, which is where the pedal bone has collapsed
What are the potential clinical signs of laminitis?
Pain
Tachycardia
Pyrexia
Bounding digital pulses
Hypermotile gastrointestinal tract
What are some of the signs that a horse is in pain due to laminitis?
Rocking back and forth
Shortened strides
Reluctant to turn
Reluctant to move at all
Reluctant to have feet picked up
Increased sensitivity to hoof testers
What are the abnormal hoof morphologies that can be indicative of laminitis?
Long toe
Short heel
Laminitic lines
Flattened or convex sole due to pedal bone collapse
Solar penetration of the pedal bone
How would you describe a horse with a laminitis score of 1 using the Obel grading scale?
Horse is frequently lifting their feet
How would you describe a horse with a laminitis score of 2 using the Obel grading scale?
Horse is willing to walk and can life forefeet however has a laminitic gait
How would you describe a horse with a laminitis score of 3 using the Obel grading scale?
Horse resists lifting forefoot and moves reluctantly
How would you describe a horse with a laminitis score of 4 using the Obel grading scale?
Horse is forced to move and may or may not be recumbent
Which factors should you focus on when doing a clinical examination of a horse with suspected laminitis?
Full clinical examination
Assess stance
Assess hoof conformation
Grade the lameness
Grade the laminitis
Digital pulses
Palpate the coronary band
Evaluate for causes of laminitis
What can be indicated on palpation of the coronary band?
If you palpate the coronary band and can produce a depression with your thumb, this is indicative of sinking of the pedal bone and you should proceed with radiography
How should you approach further investigation of acute laminitis?
Haematology and biochemistry
Radiography
Assess pasture/feed management
Why is it important to assess pasture/feed management when investigating acute laminitis?
Grain overload can cause acute laminitis
How can grain overload cause acute laminitis?
When a large amount of grain enters the hindgut, the starch will be rapidly fermented by bacteria, leading to lactic acid production by the bacteria and acidification of the enviornment which can cause dysbiosis. This can allow for the translocation of endotoxins into the blood which can cause systemic inflammation and inflammation and disruption of blood flow to the laminae, which can cause laminitis
What can be done to try and prevent laminitis if you know a horse has ingested large quantities of grain?
Continuous icing on the hooves can reduce the risk of laminitis
How should you approach further investigation of chronic laminitis?
Haematology and biochemistry
Radiography
Serum insulin levels
Test for equine metabolic syndrome (EMS)
Test for equine pars intermedia dysfunction (PPID)
What is the purpose of radiography when investigating laminitis?
Radiography can be used to establish the severity of the laminitis and to plan future farriery
How do you treat laminitis?
Box rest
Reduce further absorption of non-structural carbohydrates
Decrease stress on the laminae
Analgesia
Cryotherapy
Dietary management
Farriery
How long should you box rest horses with laminitis?
Horses with laminitis should be on box rest for six weeks from cessation of clinical signs
How can you reduce absorption of non-structural carbohydrates in horses with laminitis?
Remove horse from pasture
Liquid paraffin to reduce absorption
Activated charcoal to reduce absorption
What can be done to reduce the stress on the lamellae in laminitis horses?
Remove shoes
Provide deep supportive bedding
Box rest
Hoof and solar support
Which analgesic options are appropriate for managing laminitis in practice?
NSAIDS
Opioids
Acepromazine
Paracetamol
Aspirin
Gabapentin
Use an appropriate multimodal analgesia apprach for laminitis
Which NSAIDS are the most appropriate for management of laminitis?
Ketoprofen
Flunixin
What are the benefits of ketoprofen and flunixin when managing laminitis?
Ketoprofen and flunixin provide potent and reliable analgesia and anti-inflammatory effects
Which opioids are the most appropriate for the management of laminitis?
Buprenorphine
Morphine
What are the benefits and limitations of using buprenorphine in the management of laminitis?
Buprenorphine is licensed in horses and only requires doses every 12 hours which can be more practical. However, buprenorphine can cause box-walking so should always be administered in combination with a sedative
What are the benefits and limitations of using morphine in the management of laminitis?
Morphine provides very effective analgesia however is relatively short acting and requires every 4 to 6 hours which can be unpractical. Furthermore, morphine significantly reduces gastrointestinal motility so it is important to keep the patient hydrated to prevent impactions
What are the benefits of acepromazine in the management of laminitis?
Acepromazine is a sedative and thus will encourage the patient to lie down which can take the pressure off of their feet
What are the benefits of aspirin in the management of laminitis?
Aspirin is particularly useful in the management of laminitis when the horse is in a hypercoagulable state
What are the benefits of gabapentin in the management of laminitis?
Gabapentin is useful in the management of chronic laminitis and neuropathic pain
Which analgesia protocol is used in hospitalised patients with laminitis?
Morphine
Acepromazine
Lidocaine
Why is effective pain management so important in the treatment of laminitis?
Laminitis is a very painful condition, and management of pain can reduce catecholamine driven vasoconstriction which can worsen the laminitis. It has been shown that good pain management can improve the prognosis for laminitis
What is cryotherapy?
Cryotherapy is continuous icing of the hooves
What are the benefits of cryotherapy?
Cryotherapy will reduce metabolic rate, decrease glucose uptake into the laminae and decrease inflammation
Which dietary management should be carried out in laminitis patients?
Soaked roughage
Remove concentrates from the diet
Grazing muzzles if on pasture
Grazing at night if on pasture
How should you monitor the progression of laminitis?
Do radiograph re-evaluation to see if the new hoof horn is developing parallel to the surface of the pedal bone
Which conditions are commonly associated with laminitis?
Obesity
Equine metabolic syndrome (EMS)
Equine pars intermedia dysfunction (PPID)
What type of control is exerted on the pars intermedia in a normal, healthy horse?
In healthy, normal horses the pars intermedia is under dopaminergic control from the hypothalamus
How does the dopaminergic control of the pars intermedia differ in autumn in normal, healthy horses?
In the autumn, most healthy horses have a decrease in dopaminergic control of the pars intermedia which allows for increased growth of the hair coat and increased fat deposition
What is the pathophysiology of equine pars intermedia dysfunction (PPID)?
Equine pars intermedia dysfunction (PPID) is when there is decreased dopaminergic control exerted on the pars intermedia all year round. Without this inhibition, melanotrophs of the pars intermedia synthesise excessive hormone, including ACTH, MSH and β-endorphins in combination with hyperplasia and the development of micro- and macro-adenomas. This can cause compression of the hypothalamus which can contribute to clinical signs
Which age group of horses are commonly affected by equine pituitary pars intermedia dysfunction (PPID)?
Older horses (12 years and older)
What are the clinical signs of equine pars intermedia dysfunction (PPID)?
PUPD
Abnormal fat deposition
Muscle wastage
Laminitis
Hyperhidrosis
Hypertrichosis
Retention of water coat
Immunosuppression
Intermittent collapse
Altered demeanour
What is one of the characteristic signs of abnormal fat deposists in patients with equine pars intermedia dysfunction (PPID)?
Buldging supraorbital fat pads
What are some of the key signs of immunosuppression in patients with equine pars intermedia dysfunction (PPID)?
Non-healing wounds
Increased susceptibility to infections
Increased faecal egg count
What causes intermittent collpase in equine pars intermedia dysfunction (PPID) patients?
Compression of the hypothalamus by the pituitary gland can cause intermitten collapse
Which tests can be done to diagnose equine pars intermedia dysfunction (PPID)?
Basal ACTH concentration
TRH stimulation test
Altered dynamic insulin response
What causes the altered dynamic insulin response in equine pars intermedia dysfunction (PPID)?
Equine pars intermedia dysfunction (PPID) cause increased secretion of ACTH which will trigger excess cortisol which will cause insulin resisance and alter the dynamic insulin response. It is important to note that the insulin will not normalise until the ACTH levels are normalised
How do you measure basal ACTH concentration in a horse?
Take a blood sample and place it into an EDTA tube. Centrifuge the sample and freeze it to be sent to the lab. The lab will interpret based on a reference range which accounts for the seasonal changes in ACTH
When is a TRH stimulation test indicated?
A TRH stimulation test is indicated if the results for the plasma ACTH levels were equivocal
How do you carry out a TRH stimulation test on a horse?
- Take a sample to measure the basal ACTH levels
- Administer 1mg of TRH intravenously
- Resample for plasma ACTH levels after ten minutes. There will be a significant increase in ACTH in horses with equine pars intermedia dysfunction (PPID)
How do you treat equine pars intermedia dysfunction (PPID)?
Dopamine agonist
Which dopamine agonist is used in the treatment of equine pars intermedia dysfunction (PPID)?
Pergolide
Why is it important to introduce pergolide treatment gradually?
It is important to introduce treatment with pergolide gradually as rapid introdiction of pergolide can result in diarrhoea
(T/F) Pergolide treatment can be stopped once the laminitis secondary to PPID is resolved
FALSE. Pergolide is a lifelong treatment which will most likley require increased dosing as the pars intermedia will continue to increase in size
How should you monitor patients on pergolide treatment?
Assess for improvement in clinical signs and plasma ACTH concentrations 6 weeks after beginning treatment, then again on a 6 monthly basis
