Hepatic Disease in Horses Flashcards
when is function impaired in hepatic mass loss?
80% of hepatic mass lost
why can liver disease cause anorexia?
accumulation of waste products suppressing appetite centers
what are the three main pathways for icterus in horses?
anorexia-associated
hemolysis
cholestasis (liver disease)
what is hepatic encephalopathy?
abnormal mental status that accompanies severe hepatic insufficiency
what is hepatic photosensitization due to?
increased phylloerythrin in skin
what are the two differential diagnoses for photosensitization?
healthy horse consuming photosensitizing plants- eating normally
liver disease- anorexia and weight loss too
which clotting factors does the liver normally synthesize?
fibrinogen
factors II, VII, IX, X, protein C
where is lactulose metabolized?
colon
why does unconjugated bilirubin rise in decreased liver function?
decreased hepatic uptake
what are normal bile acid levels?
<11 micromol/L
what should you assess the liver for with ultrasonography?
right and left liver
size, shape, position, echogenicity
what information can liver biopsy give?
diagnostic
prognostic
what is the cause of the majority of liver diseases in horses?
bacterial
what causes tyzzer’s disease?
Clostridium piliforme
what is bacterial hepatitis/cholangiohepatitis diagnosed based on?
histopathology and culture of liver biopsy samples
what type of disease is parasitic hepatitis usually?
focal disease only
what can cause acute biliary obstruction?
large colon torsion
torsion of liver lobe (extremely rare)
secondary to cholelithiasis
what causes hepatic lipidosis?
negative energy balance
lipid accumulation in blood (hyperlipidemia)
lipid infiltration of liver, kidneys, intestine
what is the treatment of theiler’s disease/equine parvovirus-hepatitis?
supportive care
what does pyrrolizidine alkaloid toxicity cause?
chronic megalocytic hepatotoxicity
clinical signs 4 weeks-12 months later: hepatic failure
what is seen on biopsy of pyrrolizidine alkaloid toxicity?
classic triad:
megalocytosis
biliary hyperplasia
bridging fibrosis
when do you see clinical signs with clover poisoning?
2 weeks after consumption
diet at least 20% clover
what is the treatment for cholelithiasis?
long-term antibiotics
what can occur in older horses?
atrophy of right liver lobe
what causes yellowing of sclera from grazing on green pasture?
xanthophylls in grass
what are the three main pathophysiological mechanisms of hepatic encephalopathy?
ammonia toxicity to cell and accumulation of glutamate once astrocytes damaged
aromatic amino acids acting as false neurotransmitters
activation of central GABA-benzodiazepine receptors
inflammation also plays role
what can be abnormal in clotting in liver disease?
prothrombin time
activated partial thromboplastin time
how can we treat hepatic insufficiency?
supportive therapies
IV fluids
IV dextrose/glucose
anti-inflammatory drugs
milk thistle
S-adenosylmethionine
why would we give lactulose for hepatic encephalopathy?
decreases ammonia absorption
how does lactulose decrease ammonia absorption?
metabolized to volatile fatty acids in colon: lowers pH
ammonia converted to NH4+ and trapped in gut lumen
what are some tests for liver function?
unconjugated and conjugated bilirubin
bile acids
ALP
what are some tests for liver damage?
AST
GGT
SDH
LDH (-5)
GLDH
bile acids above _________ are highly specific for liver disease/dysfunction
20 micromol/L
what are the negatives of doing a liver biopsy?
hemorrhage risk
often histopath does not give definitive diagnosis
where is a liver biopsy done?
right 12-14 intercostal spaces
ultrasound guided
what are some chronic liver diseases?
pyrrolizidine alkaloid toxicity
clover poisoning
chronic active hepatitis
cholelithiasis
abscess
neoplasia
what are some acute liver diseases?
bacterial
parasites
toxins
acute biliary obstruction
hepatic lipidosis
viral diseases
who gets tyzzer’s disease?
foals 7-42 days
what does tyzzer’s disease cause?
acute hepatic failure
not contagious
what usually causes bacterial hepatitis/cholangiohepatitis?
ascending infection
usually common enteric organisms
what can cause parasitic hepatitis?
Parascaris equorum
Strongylus edentatus or equinus
S. vulgaris
Echinococcus granulosa
liver fluke
what are some hepatic viral diseases?
non-primate hepacivirus
equine parvovirus-hepatitis: theiler’s
equine pegivirus
what are the clinical signs of theiler’s disease/equine parvovirus-hepatitis?
acute to subacute hepatic failure
2-7 days
what is the prognosis of theiler’s disease?
guarded
what is seen on histopathology with theiler’s disease?
widespread centrilobular to midzonal hepatocellular necrosis with hemorrhage, lymphocytic/plasmocytic infiltration
what is cholelithiasis associated with?
bacterial infection
