7.1.1: Hepatic causes of weight loss including diagnosis and treatment

Question 1

Give examples of hepatic diseases that lead to weight loss

Answer 1

• Theiler’s disease/serum-associated hepatitis
• Ragwort poisoning
• Cholangiohepatitis
• Cholelithiases

Question 2

How does weight loss result from hepatic disease?

Answer 2

• Clinical signs are seen in hepatic failure - when 75+% of the liver is damaged
• Weight loss may result from anorexia or abnormal metabolism

Question 3

Clinical signs of hepatic disease

Answer 3

Weight loss - due to:
* Anorexia or altered metabolism

Colic, diarrhoea, ascites - due to:
* Hepatic swelling
* Portal hypertension
* Altered microflora
* Abnormal bile acids

Question 4

How does hepatic encephalopathy develop?

Answer 4

• GI-derived neurotoxins (NH3)
• Increased GABAergic tone
• Altered benzodiazepine receptors
• Increased neurosteroid synthesis
• Increased managanese (neuronal loss)
• False neurotransmitters
• Increased cytokines
• Increased BBB permeability and altered energy metabolism

Question 5

Cause and pathogenesis of Theiler’s disease

Answer 5

• Equine blood products cause acute hepatitis
• Causative agents: equine parvovirus shows evidence of association, as does equine hepacivirus

Question 6

What are some other names for Theiler’s disease?

Answer 6

Theiler’s disease = serum-associated hepatitis

Question 7

Ragwort poisoning is also known as

Answer 7

pyrrolizidine alkaloid toxicosis

Question 8

True/false: horses will readily eat growing ragwort.

Answer 8

(Usually) false - it is not palatable.
Contaminated feed/cut and dried ragwort in hay is usually the cause of poisoning

Question 9

Cholangiohepatitis

Answer 9

• Asscending bacterial infection
• Common causative agents: Salmonella spp., Klebsiella spp., E. coli and others
• Sepsis can occur after disease has spread to the liver

Question 10

Cholelithiasis

Answer 10

Stone formation in the biliary ducts causing obstruction
* Aetiology unknown
* (Previous) bacterial infection is a component of disease and is strongly associated with the later appearance of choleliths

Question 11

Good idea to eat this?

Answer 11

No
= ragwort poisoning a.k.a. pyrrolizidine alkaloid toxicosis

Question 12

Answer 12

Cholelithiasis

Question 13

Answer 13

Cholelithiasis

Question 14

What history questions are important in a weight loss investigation with a possible hepatic/intestinal cause?

Answer 14

• Signalment
• Length of weight loss
• Environmental and pasture managament - type of pasture, size, grass coverage and species, weeds, trees
• If sharing pasture with other horses (how many?) or other animal species
• Diet: amount and frequency
• Worming history
• Dental care
• Episodes of diarrhoea/soft manure/inappetance/colic

Question 15

True/false: mild elevations in liver values (SDH, GGT, AST, bile acids) are specific for liver disease

Answer 15

False
* Mild elevations in liver values are seen in chronic enteropathies
* Moderate-marked elevations are consistent with liver aetiology

Question 16

SDH

Answer 16

most sensitive marker of hepatocyte damage; complicated to interpret in practice due to low stability in plasma

Question 17

Clinical signs of hepatic insufficiency

Answer 17

(Usually non-specific)
* Depression
* Anorexia
* Weight loss
* Abdominal discomfort (colic)
* Icterus
* Fever
* Photosensitisation in white areas/mucosa
* Hepatic encephalopathy -> circling, walking compulsively, head pressing

Question 18

What clinical sign is depicted here?

Answer 18

Photosensitisation

Question 19

1

Answer 19

SDH

Question 20

2

Answer 20

AST

Question 21

3

Answer 21

GGT

Question 22

4

Answer 22

ALP

Question 23

5

Answer 23

Bile acids

Question 24

6

Answer 24

Bilirubin

Question 25

True/false: total bilirubin is a reliable marker of liver disease in horses.

Answer 25

False
Moderate elevations in total bilirubin are produced as a result of anorexia.
Total bilirubin only becomes elevated in chronic liver disease.

Question 26

What might you be able to identify on liver ultrasound?

Answer 26

• Masses
• Dilated biliary ducts
• Stones
• Changes in echogenicity suggestive of fat infiltration/fibrosis

Image = normal

Question 27

Where would we take a liver biopsy from and why would we do this?

Answer 27

• ICS 14-15 o RHS
• Liver biopsy can tell us whether the primary insult is bacterial (e.g. Clostridia, Klebsiella, E. coli, Salmonella), viral (e.g. Equine parvovirus-hepatitis virus) or toxic (e.g. mycotoxins, pyrrolizidine, iron toxicity)

Question 28

Treatment of pyrrolizidine alkaloid toxicity

Answer 28

• This causes irreversible liver damage
• Take liver biopsy to aid establishment of prognosis
• Can use antifibrotic agents e.g. steroids (dexamethasone IM or PO, prednisolone PO) or colchicine (PO)

Question 29

Treatment of cholangiohepatitis

Answer 29

• Ideally antibiotic choice should be guided by liver biopsy C&S
• Broad spectrum with good gram negative coverage ± anaerobes

Options
* When oral therapy is preferred: TMPS PO
* Fluroquinolines e.g. enrofloxacin PO
* Cephalosporins IV/IM
* ± metronidazole PO

Therapy should be continued for 2-4 weeks until there is a normal liver biopsy and no fever

C&S: culture and sensitivity

Question 30

Treatment of cholelithiasis

Answer 30

• Broad spectrum antibiotics (same as for cholangiohepatitis)
• DMSO IV for 3-5 days -> may aid dissolving of intrabiliary sludge and bilirubinate stones
• Can do laser therapy for larger stones
• Generally medical treatment has a good success rate
• Cholodectholithripsy/ cholodecholithomy is possible but has limited success

Question 31

Describe the general principles of treatment of hepatic disease in horses

Answer 31

• Remove the instigating cause if possible
• Provide supportive care: Vitamin E, Milk thistle extracts, S-adenosylmethionine, N-acetylcysteine
• Reduce the metabolic work of the liver by limiting fat and protein in the diet
• Use anti-fibrotic agents to slow the progression of disease

Question 32

Describe the changes you would make to a horse’s diet if they have hepatic disease

Answer 32

Summary: low protein and fat to reduce metabolic work of liver
* High carbohydrates (be careful in obese/laminitic horses where these need to be under strict control)
* Low protein: high branched amino acid: aromatic acid ratio (add in beet pulp, cracked corn)
* Small frequent feeding to reduce glucogenic load
* Avoid alfafa and legume type grasses due to high protei
* Can inject Vitamin B to help