7.1.1: Hepatic causes of weight loss including diagnosis and treatment Flashcards
Give examples of hepatic diseases that lead to weight loss
- Theiler’s disease/serum-associated hepatitis
- Ragwort poisoning
- Cholangiohepatitis
- Cholelithiases
How does weight loss result from hepatic disease?
- Clinical signs are seen in hepatic failure - when 75+% of the liver is damaged
- Weight loss may result from anorexia or abnormal metabolism
Clinical signs of hepatic disease
Weight loss - due to:
* Anorexia or altered metabolism
Colic, diarrhoea, ascites - due to:
* Hepatic swelling
* Portal hypertension
* Altered microflora
* Abnormal bile acids
How does hepatic encephalopathy develop?
- 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
Cause and pathogenesis of Theiler’s disease
- Equine blood products cause acute hepatitis
- Causative agents: equine parvovirus shows evidence of association, as does equine hepacivirus
What are some other names for Theiler’s disease?
Theiler’s disease = serum-associated hepatitis
Ragwort poisoning is also known as
pyrrolizidine alkaloid toxicosis
True/false: horses will readily eat growing ragwort.
(Usually) false - it is not palatable.
Contaminated feed/cut and dried ragwort in hay is usually the cause of poisoning
Cholangiohepatitis
- Asscending bacterial infection
- Common causative agents: Salmonella spp., Klebsiella spp., E. coli and others
- Sepsis can occur after disease has spread to the liver
Cholelithiasis
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
Good idea to eat this?
No
= ragwort poisoning a.k.a. pyrrolizidine alkaloid toxicosis
Cholelithiasis
Cholelithiasis
What history questions are important in a weight loss investigation with a possible hepatic/intestinal cause?
- 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
True/false: mild elevations in liver values (SDH, GGT, AST, bile acids) are specific for liver disease
False
* Mild elevations in liver values are seen in chronic enteropathies
* Moderate-marked elevations are consistent with liver aetiology
SDH
most sensitive marker of hepatocyte damage; complicated to interpret in practice due to low stability in plasma
Clinical signs of hepatic insufficiency
(Usually non-specific)
* Depression
* Anorexia
* Weight loss
* Abdominal discomfort (colic)
* Icterus
* Fever
* Photosensitisation in white areas/mucosa
* Hepatic encephalopathy -> circling, walking compulsively, head pressing
What clinical sign is depicted here?
Photosensitisation
1
SDH
2
AST
3
GGT
4
ALP
5
Bile acids
6
Bilirubin
True/false: total bilirubin is a reliable marker of liver disease in horses.
False
Moderate elevations in total bilirubin are produced as a result of anorexia.
Total bilirubin only becomes elevated in chronic liver disease.
What might you be able to identify on liver ultrasound?
- Masses
- Dilated biliary ducts
- Stones
- Changes in echogenicity suggestive of fat infiltration/fibrosis
Image = normal
Where would we take a liver biopsy from and why would we do this?
- 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)
Treatment of pyrrolizidine alkaloid toxicity
- 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)
Treatment of cholangiohepatitis
- 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
Treatment of cholelithiasis
- 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
Describe the general principles of treatment of hepatic disease in horses
- 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
Describe the changes you would make to a horse’s diet if they have hepatic disease
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
