Final Exam - Equine Hepatic Disorders Flashcards
what are the functions of the equine liver?
synthesis of 90% of plasma proteins
gluconeogenesis
elimination of ammonia - urea cycle
carb/lipid metabolism
bile excretion
conjugation of bilirubin
detoxification
vitamin/mineral storage & synthesis mononuclear phagocyte system
fetal hematopoiesis
what are some examples of causes of focal to multifocal liver injury?
abscess, infarction, & neoplasia
what are some examples of causes of acute generalized liver injury?
infection, necrosis, inflammation, & toxins
what are some examples of causes of chronic generalized liver injury?
hypoxia, inflammation, cholangitis, neoplasia, & toxins
what is hepatic insufficiency? how much damage must occur for this to become apparent in horses?
inability of the liver to perform its normal functions
loss of > 80% hepatic mass - liver has tremendous reserve capacity
why may you not see signs of hepatic insufficiency in horses?
hepatic regeneration may parallel hepatic destruction
T/F: to see clinical signs associated with liver disease, there must be a loss of > 80% hepatic mass with signs being abrupt (acute on chronic)
true
what are the main clinical signs associated with hepatic disease in horses?
lethargy, anorexia, & weight loss
sometimes icterus
other than liver disease, what else can cause icterus in horses?
hemolysis & anorexia
what are some less common clinical signs of hepatic disease?
photosensitization, ascites, hemolysis
what is hepatic encephalopathy?
complex syndrome characterized by abnormal mental status that accompanies hepatic insufficiency, augmented neuronal inhibition, & is potentially reversible
what is the 2nd stage of hepatic encephalopathy seen in horses?
drowsiness/disorientation, lethargy/depression, head-pressing, ataxia/aimless walking, excessively yawning, & personality/behavior changes
what is the 3rd stage of hepatic encephalopathy?
somnolence/stupor, & episodes of uncontrolled aggressive behavior
what is the 4th stage of hepatic encephalopathy?
coma, rarely seizures, & death
what is the pathophysiology of hepatic encephalopathy?
gut derived neurotoxins - ammonia & mercaptans
false neurotransmitters - decrease branched-chain AA & increase aromatic AA
- augmented inhibitory gaba activity
- increased permeability of the blood brain barrier
- impaired CNS energy metabolism
what are your big tools for evaluating liver disease in horses?
history/physical exam - ultrasound/biopsy
evaluation of bilirubin
liver enzymes/liver function
what are your main liver function tests?
serum bile acids, ammonia, & coagulation panel
what is the most liver-specific enzyme in horses?
IDH
normal < 6 u/L - foals under 4 weeks will have higher normals
few hours for 1/2 life
why do we see increases of ALKP in horses?
induction - cholestasis, glucocorticoids, phenobarbitol
why is ALKP normally elevated in foals?
osteoblastic activity
T/F: ALKP is liver-specific
false - bone, intestine, kidney, placenta, & WBC
elevations of ALKP in adult horses are likely caused by what?
cholestasis or chronic liver disease
T/F: AST is sensitive for liver disease but not specific
true - remains elevated several days after the problem has resolved
T/F: cholestasis can cause increased GGT
true
where is GGT released from?
microsomal membranes of biliary epithelium
T/F: GGT is liver-specific except for the pancreas
true
GGT levels have a higher normal in foals or adult horses?
foals < 45 days
what are the 5 isoenzymes of LDH? which one is an indicator of acute hepatocellular disease?
liver, muscle, RBC, intestine, & kidney
LDH-5
T/F: ALT is useful for assessing liver disease in horses
false - not helpful
an increase in ________ bilirubin suggests liver disease?
conjugated
what defines hyperbilirubinemia?
> 5mg/dl
what are some potential causes of hyperbilirubinemia?
hemolysis, anorexia, & hepatobiliary disease
T/F: a serum bile acid concentration test is highly specific for liver disease & highly sensitive for detecting liver dysfunction
true
why should you run a coagulation panel in a horse that you think may have liver disease?
the liver synthesizes coagulation factors - need to run prior to a biopsy
where is the liver located on the right side of the horse?
just caudal & ventral to the lung field - may see normal hepatic atrophy in older horses
where is the liver located on the left side of the animal?
cranial aspect of the abdomen just ventral to diaphragm & adjacent to the spleen
what type of transducer should you use for a liver ultrasound? what frequency?
curvilinear probe - 3.5-5.0 frequency
what will hepatic fibrosis look like on ultrasound?
hyperechoic liver
should the liver be hypoechoic or hyperechoic compared to the spleen?
hypoechoic
what is this?
starry sky liver - multifocal granulomas in horses
is this liver normal? why?
no - hyperechoic to spleen
what are the risks associated with a liver biopsy?
pulmonary hemorrhage, hepatic hemorrhage, pneumothorax, peritonitis (bile leakage/colon puncture)
ultrasound guided minimizes risks
what is the goal of treating hepatic disease in horses?
support the patient until the liver regenerates - fluids/electrolytes, acid/base support, dextrose infusion (help decrease liver work load)
how can you help reduce production & absorption of ammonia in a horse with hepatic disease?
mineral oil via NG tube, neomycin, & metronidazole, lactulose syrup to reduce colonic pH/ammonia trapping
what does the dietary management of hepatic disease include for horses?
low protein, high carb, rich in branched chain amino acids - no alfalfa hay
why avoid diazepam for a horse with hepatic encephalopathy?
liver metabolizes the drug - use xylazine instead
