Equine liver disease + hyperlipidaemia

Question 1

What is the function of the equine liver?

Answer 1

• Digestive and secretory (bile salts)
• Metabolic (CHO, protein, fat metabolism)
• Detoxification/excretory (first pass from GIT)
• Synthetic (clotting factors, proteins)
• Storage (vitamins, minerals)

Question 2

What is jaundice?
Ddx for jaundice?

Answer 2

• Retention of bilirubin - unconjugated predominant in horses
• Ddx = Anorexia, Haemolysis, Liver failure

Question 3

What are CS of liver disease - may not always be present?

Answer 3

• Jaundice
• Weight loss
• Depression / CNS signs (central blindness / head pressing, yawning)
• Skin lesions
• Haemorrhage
• Colic
• Oedema
• Diarrhoea
• Bilateral laryngeal paralysis

Question 4

What skin lesions are seen in horses?

Answer 4

• Hepatic photosensitisation
• phylloerythrin accumulation - activated by UV light
• Ddx primary phtosensitisation = tetracyclines or st johns wort
• Ddx immune mediated vasculitis
• Ddx contact - clover

Question 5

What are liver specific enzymes?

Answer 5

• GGT
• SDH
• GLDH

Question 6

What are non liver specific enzymes?

Answer 6

• AST + muscle
• ALP + bone, intestine, kidney, placenta, leukocytes
• LDH-5 + muscle

Question 7

What enzyme is most sensitive to liver disease?

Answer 7

• GGT - increases in all types of liver disease

Question 8

What are some liver function tests?

Answer 8

• Bile Acids = biological detergent
  – Absorption of lipids \ lipid soluble vitamins etc
  – Excretion of cholesterol
  – 90% of bile acids get reabsorbed in SI, returns via enterohepatic circulation
  – Liver failure – decreased absorption
• Bilirubin (total, conjugated and unconjugated)
  – Unconjugated:
  *Liver failure, haemolysis, anorexia, intestinal obstruction, Gilbert’s syndrome
  *Associated with poorer outcome in one paper
  – Conjugated:
  *>25% of total bilirubin: hepatocellular failure
  *>30% of total bilirubin: choleostasis
• Ammonia
  – RBCs produce NH3
  – Measure within 15mins
  – If not, separate plasma within 15 min
  – Keep on ice / freeze
  – Keep tube stoppered
• Urea decreases - Lack of ammonia metabolism
• Globulins increase - Failure of Kupffer cells to remove intestinal antigens
• Triglycerides increase - Inadequate carbohydrate metabolism and gluconeogenesis
• Decrease synthesis of proteins - E.g. clotting factors, albumin

Question 9

Where would you take biopsy?

Answer 9

RHS
* Shoulder + elbow – tuber coxae
* ICS 7ish – 15ish
* Ventral lung – costochondral junction
LHS
* ICS 6ish – 9ish
* Adjacent to spleen

-find on ultrasonography first

Question 10

What is the pathogenesis of ragwort poisoning?

Answer 10

• Pyrrolizidine alkaloid toxicity
• Megalocytosis, fibrosis + persistent toxic effect
• more commonly ingested in hay
• Usually only showing signs prior to death >70% loss of liver function - weight loss, behavioural change, anorexia

Question 11

How would you treat ragwort?

Answer 11

• Supportive tx = fluid therapy, electrolytes, glucose
• Drugs to reduce production of ammonia - metronidazole

Question 12

What can a horse with Cholangiohepatitis or cholelithiasis present with?

Answer 12

• Fever - ascending infection
• Jaundice
• colic

Question 13

How would you treat chronic active hepatitis?

Answer 13

• Corticosteroids (prednisolone) or immunosuppressive meds (azathioprine)

Question 14

What can cause acute hepatitis?

Answer 14

• Theiler’s disease-associated virus
• Other viruses – parvovirus, hepacivirus
• Aflatoxins
• Liver fluke (Fasciola hepatica)
• Range from mild to severe CNS signs, jaundice and discoloured urine

Question 15

How would you manage hepatic encephalopathy?

Answer 15

• Avoid sedation but if required – alpha -2 agonist, not diazepam
• Reduce production of neurotoxins
  » Metronidazole – decrease ammonia producing bacteria
  » Lactulose
  -Poorly digested /absorbed carbohydrate
  -Increases H+ production
  -NH3 converted to NH4+
• Fluid balance, regulate glucose and sodium balance

Question 16

How would you reduce inflammation + fibrosis?

Answer 16

• Prednisolone/dexamethasone
• Silymarin (milk thistle)

Question 17

How would you manage a diet in a liver disease horse?

Answer 17

• Carbohydrate- based feed – maintain/gain weight
• Moderate quantities of high quality protein (branch chain amino acids, not aromatic)
  – Legume, grass, wheat bran, maize
• Fat soluble vitamin supplementation

Question 18

What are risk factors of hyperlipaemia?

Answer 18

• Breed
• Obesity
• Females
• Age vs insulin sensitivity
• Underlying disease
• Transport, stress, lactation
• Starvation

Question 19

What is the breakdown of hyperlipaemia?

Answer 19

• Breakdown of stored fat (HSL) - FA’s to liver - energy
• Liver poor ketogenic capability, energy production overwhelmed
  – triglycerides accumulate in liver and in plasma
• Ideally want to promote re-uptake in periphery by LPL - clear plasma

Question 20

How does hyperlipaemia present?

Answer 20

• Non-specific: anorexia, lethargy, weakness
  – progress to more severe CNS & other signs
• Signs may be underlying disease, hyperlipaemia or secondary liver disease
• Need to be aware of at risk animals

Question 21

How is hyperlipaemia diagnosed?

Answer 21

• Cloudy serum
• TG’s >5mmol/l = hyperlipaemia
• TG’s <5 (but >1.5) = hyperlipidaemia

Question 22

What is Tx of hyperlipaemia?

Answer 22

• Treat underlying disease +parasites
• POSITIVE ENERGY BALANCE
• Correction of dehydration, electrolyte imbalances, acidosis
• Other symptomatic therapy
• Normalisation of lipid metabolism
• Poor prognosis