Hepatic Disease - Equine Flashcards
The liver accounts for what percentage of an adult horse’s body weight?
1.6%
What are the functions of the liver?
- processing nutrients from food
- storing glucose, vitamins, and minerals
- maintaining immune function
- removing toxins from the blood
What percentage of the horse’s total blood volume resides in the liver?
10%
How much of the liver must be damaged before there is abnormal function or failure?
70-80%
What are the general clinical signs of acute liver dysfunction?
- depression
- HE
- icterus
- colic
- anorexia
What is indicated by a high level of fibrinogen?
Low level?
high - inflammatory process
low - issues with production in liver
What is indicated by elevated bilirubin?
- liver failure
- bile blockage
- excess production
Which enzymes can be used to evaluate liver function?
SDH
ALP
AST
GGT
Which coagulation factors are produced in the liver?
I, II, V, VII, IX, and X
Where should the ultrasound probe be positioned to evaluate the liver?
right side, caudal to the lungs, in the 6th to 14th intercostal spaces
What are the possible causes of icterus/jaundice?
decreased excretion or increased production of bilirubin
What is photosensitization type 1?
primary photodynamic agent enters skin by ingestion
What is photosensitization type 2?
- accumulation of endogenous photodynamic agents
- congenital prophorias
What is photosensitization type 3?
hepatogenous secondary photosensitization
- phylloerythrin
What are the clinical signs associated with photosensitization type 3?
- erythema initially
- edema
- sloughing and exposure of subcutaneous tissue
How is photosensitization treated?
- eliminate photodynamic agent
- remove animal from sunlight
- treat as skin burn
What is hepatic encephalopathy?
- neuropsychiatric syndrome secondary to hepatic insufficiency
- CNS characteristics
What are the clinical signs associated with hepatic encephalopathy?
- frequent yawning
- abnormal behavior
- aimless wandering and foot stomping
- head pressing, circling, seizures
Describe the proposed pathophysiology of hepatic encephalopathy
- decreased branched-chain amino acids, and increased aromatic amino acids
- aromatic amino acids cross BBB into CNS
- increase inhibitory neurotransmitters
- increase GABA and L-glutamate
- imbalance of inhibitory and excitatory neurotransmitters
How is hepatic encephalopathy treated?
- eliminate underlying cause
- supplement with branched amino acids
- low protein, high carb diet
- avoid alfalfa
- supportive therapy
What is idiopathic acute hepatic disease?
- Theiler’s disease or serum sickness
- most common cause of acute hepatitis and hepatic failure in horses
What are the possible causes of IAHD?
- viral infection
- tetanus antitoxin
- hypersensitivity type 3
- dietary factors
- pyrrolizidine alkaloid toxicity
What are the clinical signs associated with IAHD?
- abrupt presentation
- CNS signs
- yawning as early sign
- photodermatitis
- intravascular hemolysis
- weight loss and ventral edema
What are the hematology/chem features of IAHD?
- elevated bilirubin, AST, SDH, and GGT
- increased bile acids
- decreased BUN
- hyperammonemia
- prolonged clotting time
What are the histopathologic features of IAHD?
- hepatocellular necrosis
- portal accumulation of mononuclear cells and neutrophils
- proliferation of bile ductules
Which disease results in a “dishrag” liver?
idiopathic acute hepatic disease (IAHD)
What is choledocholithiasis?
stone found in the common bile duct
What is hepatolithiasis?
presence of calculi in the intrahepatic bile duct
What are the possible causes of cholelithiasis?
- ascending biliary infection or inflammation
- parasites (ascarids)
- biliary stasis/reflux
- changes in bile composition
- foreign body
What are the clinical signs associated with cholelithiasis?
colic with pyrexia and icterus
What are the hematology/chem features of cholelithiasis?
- neutrophilic leukocytosis
- increased liver enzymes
- increased bile acids and bilirubin
- hyperammonemia
- prolonged clotting time
What are the histopathological features of cholelithiasis?
- periportal fibrosis
- bile duct stasis and hyperplasia
Which bacteria can be present with cholelithiasis?
Bacteriodes vulgtus and E. coli
How is cholelithiasis treated?
- antimicrobials, fluids, anti-inflammatories, DMSA, dietary management
- choledocholithiotomy +/- choledocholithotripsy
What are the histological and gross features of chronic active hepatitis?
- infiltration of inflammatory cells into portal areas, necrosis, and fibrosis
- liver is firm, and often pale brown-green
What are the clinical signs associated with chronic active hepatitis?
- progressive weight loss
- intermittent fever
- icterus
- moist exfoliative dermatitis
- necrotic leathery skin at coronary band
How is chronic active hepatitis treated?
- supportive care
- corticosteroids
- antimicrobials
- anti-inflammatories
- Colchine
What is the action of Colchine?
inhibits production of collagen and macrophages/cytokine-induced inflammation
Describe the pathophysiology of pyrrolizidine alkaloid toxicity
- alkaloids metabolized in liver to pyrroles
- cross links DNA and causes antimitotic effect
- hepatocytes die and are replaced by fibrous tissue
- inhibition of enzymes and protein synthesis
- veno-occlusive
What is found on liver biopsy with prryolizidine alkaloid toxicity?
- fibrosis
- bile duct proliferation
- megalocytosis
What is Tyzzer’s Disease?
- bacterial hepatitis in foals
- rapidly fatal
What organism is responsible for Tyzzer’s disease?
Clostridium piliformis
What are the clinical signs associated with Tyzzer’s disease?
- sudden death
- fever, depression, anorexia, diarrhea
- icterus, hypoxia, tachypnea, seizures
What is found on hematology/chemistry with Tyzzer;s disease?
- elevated liver enzymes
- severe hypoglycemia
How is Tyzzer’s disease diagnosed?
PCR
post-mortem is the only definitive dx
- Warthin-Starry Stain
How is Tyzzer’s disease treated?
- aggressive supportive therapy
- penicillin, tetracycline, erythromycin
What are the possible causes of hepatic failure in foals?
- pre-colostral iron fumarate toxicity
- perinatal herpesvirus
- leptospirosis
- cholangitis associated with duodenal ulcers
- ascarid migration
- portosystemic shunt
- hepatotoxicity (neonatal isoerythrolysis)
What is the treatment for abnormal behavior from hepatic disease?
Xylazine
- avoid diazepam
What are the methods for decreasing blood ammonia?
- mineral oil, oral neomycin
- oral lactulose
- Metronidazole
What are the terminal signs of hepatic disease?
hemolytic crisis
severe hepatoencephalopathy with fibrotic liver
