Liver Diseases of Horses (Hostnik) Flashcards
Equine:
What empties into the duodenum at the major duodenal papilla, located on a slightly raised mucosal ridge?
Both the bile duct and pancreatic duct
Equine:
What opens at the minor duodenal papilla?
Accessory pancreatic duct
Equine Definition:
Is a complex clinical syndrome characterized by the abnormal mental status that accompanies severe hepatic insufficiency
Hepatic Encephalopathy (HE)
(T/F) Hepatic Encephalopathy generally is considered to be a potentially reversible metabolic encephalopathy
True
Acute Disease:
- Is a hepatotropic Single-stranded DNA virus capable of causing hepatitis in infected horses
- Has been found in consecutive horses with Theiler’s disease that received tetanus antitoxin or other equine-origin blood products
Equine parvovirus
Equine:
What was the first of the three new blood-borne viruses to be reported?
Nonprimate Hepacivirus
- is a flavivirus, uncommon in mules or donkeys
List the nutrient metabolism of liver functions:
- Carbohydrates
- Fat
- Protein
What are common clinical findings of liver disease in a horse?
- Depression
- Anorexia
- Colic
- Weight loss
- Icterus (important indicator)
- Pigmenturia
- Hepatic Encephalopathy (HE)
- Caused by hyperbilirubinemia
- 10-15% of horses normally have slightly yellow sclera
- related to fasting
Ictures (jaundice)
- Phylloerythin (derived from chlorophyll) is normally metabolized and excreted by the equine liver
- In disease, increases in phylloerythrin in the blood react with UV light to cause damage and necrosis of unpigmented skin
- the liver is not detoxifying that substance properly
Photosensitization
- Augmented GABA activity in the brain (sleepy horses)
- Altered expression of benzodiazepine receptors
- Increased neurosteroids (not much is known)
- False neurotransmitter accumulation
- Inflammatory mediator expression
- Increased BBB permeability and cerebral hypertension
These are other mechanisms/pathogenesis that may be involved with …
Hepatic Encephalopathy
What are the main enzymes that we look for in lab testing in a clinical assessment of the liver in horses?
- Asparte aminotransferase (AST)
- Not specific to the liver (come from muscle, RBCs) - Sorbitol dehydrogenase (SDH)
- Liver-specific in a horse
- is the main one that we look at for hepatocellular leakage
(both are hepatical leakage enzymes when the hepatocyte is damaged they leak out into the blood)
Clinical Assessment of the liver in horses
List the two enzymes that are liver-specific:
- SDH
- increases seen with ongoing injury
- shorter half-life than AST (increase quicker, and decrease quicker)
- GGT
Clinical Assessment of the liver in horses
What enzymes are biliary/cholestatic (hepatobiliary)?
- Gamma-glutamyl transferase (GGT)
- Alkaline phosphatase (ALP)
- non-specific (also bone, intestinal, renal, mammary, placenta, leukocytes, corticosteroids)
(are actually induced)
Equine Functional Tests:
- Indirect (unconjugated)
- Direct (conjugated)
- In horses with Anorexia of any cause, we see an increase in UNconjugated ___________ due to a decrease in the proteins required to import UNconjugated __________ into the liver
bilirubin (increase)
Equine Functional Tests:
- Per- and post-prandial measurement is not necessary since horses continuously secrete bile
- Horses DON’T have a gallbladder
Increase Bile Acids
Equine Functional Tests Results: Liver Disease
- Increased Bilirubin
- Increased Bile Acids
- Increased Ammonia
- Decreased UREA (BUN)
- Decreased Glucose
- Coagulation testing (depends on what you are measuring)
Bilirubin
- Hemolysis
- Fasting hyperbilirubinemia
Unconjugated (indirect)
Bilirubin
- Cholestasis
Conjugated (direct)
(T/F) Abdominal radiographs are useful to evaluate the liver in equids
False, Abdominal radiographs are NOT useful
- Chronic megalocytic Hepatopathy
- Delayed onset, chronic, progressive liver failure due to ingestion of pyrrolizidine alkaloid-containing plants
- Metabolized by the liver after ingestion into toxic pyrrole derivatives
- Alkylate nucleic acids and protein, preventing cellular replication and protein synthesis
- Causes hepatocytes to enlarge -> megalocytes
- When megalocytes die, it causes fibrosis
Pyrrolizidine Alkaloid Toxicity
Equine:
What do you see in a liver biopsy of a horse with pyrrolizidine alkaloid toxicity?
- Megalocytosis
- Biliary hyperplasia
- Fibrosis
NAVLE
- Clostridium piliforme
- Motile, pleomorphic, Gram-Negative, spore-forming, obligate intracellular bacterium
- Acute necrotizing hepatitis in FOALS (3 weeks old - between 7 & 42 days)
- Foals ingest contaminated soil or feces from the dam (relatively common in the enviroment - cases are sporadic)
- Travels to the liver and heart via lymphatics and hematogenous spread
Tyzzer’s Disease
What is the primary disease associated with Tyzzer’s Disease (highly fatal)?
Acute, multifocal hepatitis
(but also myocarditis and enteritis are seen)
-> will see grossly an enlarged, swollen lover with 1- to 5-mm white foci throughout (coagulative necrosis and inflammation)
- Serum hepatitis, serum sickness, acute hepatic necrosis
- Now –> Viral hepatitis
- Acute or subacute hepatitis with liver necrosis in Adult Horses
- Association with the administration of equine-derived biological products (typically 4-10 weeks before the onset of hepatic failure)
- Most common is Tetanus Antitoxin
Theiler’s Disease
- Likely caused by Equine Parvovirus-Hepatitis (EqPV-H) – acute hepatic necrosis and subclinical hepatitis
- Equine Hepacivirus – mild, subclinical hepatitis
Theiler’s disease
- Treatment:
- Supportive care
- Prognosis is guarded with acute disease and hepatic failure
