Hepatobiliary Disease in the Horse Flashcards
What kind of history of disease might predispose horse to liver disease?
Previous GI disorders
What is Theiler’s Disease? What are the clinical signs? How rapidly do clinical signs progress?
Acute hepatic necrosis affects adult horses
clinical signs: nonspecific, many signs
(diarrhea, anorexia, fever, lethargy, neurological signs, etc)
Clinical signs progress quickly over 2-7 days
What is the cause of Theiler’s disease?
Unknown
Commonly associated with administration of tetanus antitoxin, plasma, blood products, etc. but horses can also develop symptoms from coming in contact with horses who have received the toxin
Also thought to possibly have a viral origin (equine parvovirus)
What kind of treatment is indicated for horses with Theiler’s Disease? Do all horses recover?
Supportive treatment for clinical signs
Not all horses recover
Some do well with supportive care, some are not so lucky
Which values are elevated with subclinical Theiler’s Disease?
↑GGT/AST for months
What is seen on histopathology in Theiler’s Disease?
centrilobular hepatocellular necrosis/lymphocytic infiltrates
What is Tyzzer’s Disease? What is the agent which causes Tyzzer’s Disease? How is the infection acquired?
Acute hepatitis/septicemia which affects foals 1-6 weeks old
Caused by Clostridium piliforme
Acquired by feco-oral route from carrier mares (foals perform coprophagia)
What are the clinical signs of foals with Tyzzer’s Disease? How do they usually present?
Severe hypoglycemia
Present comatose +/- seizures
What is observed on PME of a foal with Tyzzer’s Disease?
Icteric and grossly swollen liver with multiple pale necrotic areas
How is diagnosis of Tyzzer’s usually made?
Fecal PCR available, but most diagnosis made at PME
What is the prognosis of a foal with Tyzzer’s? What is the recommended treatment?
Poor prognosis
Attempt treatment with Oxytetracyclines, Penicillin
What predisposes ponies and donkeys to hyperlipemia?
Obesity
Why are pregnant or lactating ponies more likely to develop hyperlipemia?
Negative energy balance
What should you think of as a cause for hepatic disease if multiple horses on farm are affected? Where do you need to check?
Exposure to toxic plants
Check the fields
What in the diet can cause liver disease? What do you need to check?
Mycotoxins/moldy corn (Aspergillus) can cause liver disease
Hay may be contaminated with toxic plants (Senecio - Ragwort)
Check feed stores
How does ragwort poisoning occur? What is the prognosis?
Ragwort contains toxic compounds which can cause poisoning to horses if eaten in any state. Ragwort can damage the liver, which may eventually result in severe disease and even death. Ragwort is a common weed and horses may ingest it while grazing. There is no definitive cure, guarded prognosis.
At what % of liver damage does failure occur?
Failure occurs when 50-70% of liver function is lost
What do most horses with hepatic failure present with?
Hepatic encephalopathy
What causes photosensitization in horses with hepatic disease?
Photosensitization - accumulation of the photodynamic agent phylloerythrin (from plant material which horse eats), which travels up toward the skin
What % of the liver can you image with ultrasound? What can you assess about the liver with ultrasound? What kind of sampling can you perform with U/S guidance?
Can only image ~20% of the liver
Hepatomegaly, dilated bile ducts, choledoliths, abscesses and neoplasia (also useful for guiding liver biopsy)
When should you avoid liver biopsy?
If suspected liver abscess - may miss focal lesions
What are the general principles of treatment of hepatobiliary disease in horses? what does treatment depend on?
Primarily supportive treatment based on clinical signs
Depends on whether the horse is in hepatic failure or not
What is the primary goal of treatment for a horse in hepatic failure?
Treatment is focused on managing hepatic encephalopathy and maintaining normal homeostasis until liver is able to sufficiently regenerate
The development of WHAT makes liver regeneration unlikely?
Fibrosis
Is a definitive diagnosis of liver insult usually obtained? How does this alter treatment?
Definitive diagnosis usually not obtained, which means specific treatment is usually not possible, rather non-specific treatment of liver disease is usually the option
What kind of sedation is preferred in treatment of a horse with hepatobiliary disease?
a-2 agonist (Dexmeditomidine, Meditomidine, romifidine, xylazine)
Why are phenothiazines/benzodiazepines not preferred for sedation of horses with hepatobiliary disease?
Acepromazine - lowers seizure threshold
Diazepam - augments GABA receptors, increases inhibitory input
What is the aim of fluid therapy for horses with hepatobiliary disease? What are the best fluid choices for a horse with HE?
Aim is to return horse to homeostasis
Mannitol or Hypertonic saline to treat cerebral edema in horses with HE
How do you correct hypoglycemia for horses with hepatobiliary disease?
Glucose supplementation with 50% glucose at a rate of 60 ml/kg/hr CRI
What kinds of dietary changes should be made for horses with hepatobiliary disease? Which vitamins should be supplemented? Which foods should you avoid giving?
Provide diet with adequate digestible energy and protein
Small frequent meals better
Supplement vitamins A, D, E
AVOID alfalfa and other legumes and cereal based feeds
Why is lactulose recommended for horses with hepatobiliary disease?
Lactulose
Disaccharide hydrolyzed to lactic, acetic and formic acids
Lowers colonic pH, inhibits bacterial growth, traps ammonium, acts as laxative
How does milk thistle benefit horses with hepatobiliary disease?
Silybum marianum (Milk Thistle) - associated with protection against hepatic toxins and has resulted in decreased hepatic inflammation/fibrosis
What factors impact the prognosis of horses with hepatobiliary disease?
Prognosis dependent on type/severity of liver disease +/- degree of fibrosis present
Which patients are associated with fair to good prognosis?
Any horse with acute liver disease that survives for longer than 5 days and does not have irreversible fibrosis
Which patients are associated with poor prognosis?
Persistent signs of HE despite treatment
Bridging fibrosis (irreversible)
How long after ingestion does acute ragwort poisoning-associated hepatic failure occur?
Acute - 6 months post ingestion
What kind of process is this and what is it associated with?
What is another name for cholagiohepatitis? What kind of process does this imply?
Chronic Active Hepatitis
Implies sustained inflammatory process within the liver and biliary system
What is the cause of cholangiohepatitis?
Exact cause unknown
Bacterial infection and autoimmune disease implicated
What are the clinical signs associated with cholangiohepatitis? Which values will change on BW? What changes will you see on U/S? How do you confirm a suspected diagnosis?
- Recurrent fever, colic, and icterus
- Weight loss and exfoliative dermatitis seen in some cases - Suspect if ↑ALP, ↑GGT and ↑Bilirubin
- (>30% conjugated bilirubin)
- Hepatomegaly, dilated bile ducts +/- calculi seen on ultrasound - Liver biopsy +/- culture will confirm diagnosis
What is the indicated treatment for cholangiohepatitis if lymphocytic/plasmacytic infiltrate seen on histopathology? What is the treatment otherwise?
Corticosteroids
Otherwise broad spectrum abx to target gram negative bacteria (enrofloxacin, TMPS)
What does treatment for cholangiohepatitis depend on?
Histological appearance of the lesions
What substance is useful for dissolving calculi (if present) in cholangiohepatitis?
DMSO (dimethyl sulphonamide) solubilizer of calcium
What is equine hyperlipemia? Which animals are predisoposed? How common is this condition in horses? What condition increases the risk?
Metabolic disorder that is characterized by opaque serum or plasma, serum triglycerides (TG) >500mg/dL, and fatty infiltration of liver and other organs
Ponies, donkeys and miniature horses are predisposed
RARE in horses, but obesity increases risk
What is the difference between hyperLIPEMIA and hyperLIPIDEMIA? Which is the more serious condition?
Hyperlipemia - Severe clinical syndrome (TG >500 mg/dL)
- Serum opaque, hepatic lipidosis +/- failure
Hyperlipidemia - Subclinical elevation of triglycerides (TG <500 mg/dL)
- No fatty liver, no hepatic dysfunction
How does hepatic lipidosis occur?
Disease occurs due to overproduction of triglycerides in the liver due to excess fatty acid delivery (freed from adipose tissue an an excessive rate), which leads to increased liver triglycerides = hepatic lipidosis
Is hyperlipemia a primary disease? What do you need to investigate?
No - need to find an underlying cause
What is the most common cause of hepatic failure in the UK?
Ragwort poisoning
How does inadequate nutrition lead to hyperlipemia? At what points is a horse at highest risk for hyperlipemia?
NEGATIVE ENERGY BALANCE!
Pregnancy, Lactation, History of recent transport, severe parasitism, concurrent disease
How does stress exacerbate hyperlipemia?
Glucocorticoids inhibit triglyceride removal
What are the clinical signs of hyperlipemia?
Anorexia, Depression, Icterus
Weakness +/- recumbency
Ventral edema
Fetid breath, Gray coating on tongue
+/- diarrhea, pyrexia
How do you diagnose hyperlipemia?
Blood (opaque serum or plasma)
Triglycerides >500 mg/dL (diagnostic)
Hepatic enzymes - ↑GGT, SDH, GLDH, AST
Hepatic function tests - ↑bile acids, ammonia
Liver biopsy - hepatic lipidosis
What is the treatment for hyperlipemia?
AVOID STRESS
Treat any specific underlying disease
Wean foal from affected dam
Induce foaling or abortion if dam in poor condition
Restore energy balance, encourage eating
Supportive therapy
What is the prognosis for animals with hyperlipemia?
Guarded if early
Poor once severe clinical signs apparent
Vascular thrombosis, fatty infiltration of other organs, Liver rupture risk
Hyperlipemia prevention?
Intervene EARLY if signs present
Monitor predisposed animals closely (pony, donkey, mini horse, icelandic horse)
Measure TG levels in sick ponies/donkeys
Ensure adequate nutritional intake during illness/times of stress
