Final Exam - Equine Hepatic Disorders

Question 1

what are the functions of the equine liver?

Answer 1

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

Question 2

what are some examples of causes of focal to multifocal liver injury?

Answer 2

abscess, infarction, & neoplasia

Question 3

what are some examples of causes of acute generalized liver injury?

Answer 3

infection, necrosis, inflammation, & toxins

Question 4

what are some examples of causes of chronic generalized liver injury?

Answer 4

hypoxia, inflammation, cholangitis, neoplasia, & toxins

Question 5

what is hepatic insufficiency? how much damage must occur for this to become apparent in horses?

Answer 5

inability of the liver to perform its normal functions

loss of > 80% hepatic mass - liver has tremendous reserve capacity

Question 6

why may you not see signs of hepatic insufficiency in horses?

Answer 6

hepatic regeneration may parallel hepatic destruction

Question 7

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)

Answer 7

true

Question 8

what are the main clinical signs associated with hepatic disease in horses?

Answer 8

lethargy, anorexia, & weight loss

sometimes icterus

Question 9

other than liver disease, what else can cause icterus in horses?

Answer 9

hemolysis & anorexia

Question 10

what are some less common clinical signs of hepatic disease?

Answer 10

photosensitization, ascites, hemolysis

Question 11

what is hepatic encephalopathy?

Answer 11

complex syndrome characterized by abnormal mental status that accompanies hepatic insufficiency, augmented neuronal inhibition, & is potentially reversible

Question 12

what is the 2nd stage of hepatic encephalopathy seen in horses?

Answer 12

drowsiness/disorientation, lethargy/depression, head-pressing, ataxia/aimless walking, excessively yawning, & personality/behavior changes

Question 13

what is the 3rd stage of hepatic encephalopathy?

Answer 13

somnolence/stupor, & episodes of uncontrolled aggressive behavior

Question 14

what is the 4th stage of hepatic encephalopathy?

Answer 14

coma, rarely seizures, & death

Question 15

what is the pathophysiology of hepatic encephalopathy?

Answer 15

gut derived neurotoxins - ammonia & mercaptans

false neurotransmitters - decrease branched-chain AA & increase aromatic AA

1. augmented inhibitory gaba activity
2. increased permeability of the blood brain barrier
3. impaired CNS energy metabolism

Question 16

what are your big tools for evaluating liver disease in horses?

Answer 16

history/physical exam - ultrasound/biopsy

evaluation of bilirubin

liver enzymes/liver function

Question 17

what are your main liver function tests?

Answer 17

serum bile acids, ammonia, & coagulation panel

Question 18

what is the most liver-specific enzyme in horses?

Answer 18

IDH

normal < 6 u/L - foals under 4 weeks will have higher normals

few hours for 1/2 life

Question 19

why do we see increases of ALKP in horses?

Answer 19

induction - cholestasis, glucocorticoids, phenobarbitol

Question 20

why is ALKP normally elevated in foals?

Answer 20

osteoblastic activity

Question 21

T/F: ALKP is liver-specific

Answer 21

false - bone, intestine, kidney, placenta, & WBC

Question 22

elevations of ALKP in adult horses are likely caused by what?

Answer 22

cholestasis or chronic liver disease

Question 23

T/F: AST is sensitive for liver disease but not specific

Answer 23

true - remains elevated several days after the problem has resolved

Question 24

T/F: cholestasis can cause increased GGT

Answer 24

true

Question 25

where is GGT released from?

Answer 25

microsomal membranes of biliary epithelium

Question 26

T/F: GGT is liver-specific except for the pancreas

Answer 26

true

Question 27

GGT levels have a higher normal in foals or adult horses?

Answer 27

foals < 45 days

Question 28

what are the 5 isoenzymes of LDH? which one is an indicator of acute hepatocellular disease?

Answer 28

liver, muscle, RBC, intestine, & kidney LDH-5

Question 29

T/F: ALT is useful for assessing liver disease in horses

Answer 29

false - not helpful

Question 30

an increase in ________ bilirubin suggests liver disease?

Answer 30

conjugated

Question 31

what defines hyperbilirubinemia?

Answer 31

> 5mg/dl

Question 32

what are some potential causes of hyperbilirubinemia?

Answer 32

hemolysis, anorexia, & hepatobiliary disease

Question 33

T/F: a serum bile acid concentration test is highly specific for liver disease & highly sensitive for detecting liver dysfunction

Answer 33

true

Question 34

why should you run a coagulation panel in a horse that you think may have liver disease?

Answer 34

the liver synthesizes coagulation factors - need to run prior to a biopsy

Question 35

where is the liver located on the right side of the horse?

Answer 35

just caudal & ventral to the lung field - may see normal hepatic atrophy in older horses

Question 36

where is the liver located on the left side of the animal?

Answer 36

cranial aspect of the abdomen just ventral to diaphragm & adjacent to the spleen

Question 37

what type of transducer should you use for a liver ultrasound? what frequency?

Answer 37

curvilinear probe - 3.5-5.0 frequency

Question 38

what will hepatic fibrosis look like on ultrasound?

Answer 38

hyperechoic liver

Question 39

should the liver be hypoechoic or hyperechoic compared to the spleen?

Answer 39

hypoechoic

Question 40

what is this?

Answer 40

starry sky liver - multifocal granulomas in horses

Question 41

is this liver normal? why?

Answer 41

no - hyperechoic to spleen

Question 42

what are the risks associated with a liver biopsy?

Answer 42

pulmonary hemorrhage, hepatic hemorrhage, pneumothorax, peritonitis (bile leakage/colon puncture) ultrasound guided minimizes risks

Question 43

what is the goal of treating hepatic disease in horses?

Answer 43

support the patient until the liver regenerates - fluids/electrolytes, acid/base support, dextrose infusion (help decrease liver work load)

Question 44

how can you help reduce production & absorption of ammonia in a horse with hepatic disease?

Answer 44

mineral oil via NG tube, neomycin, & metronidazole, lactulose syrup to reduce colonic pH/ammonia trapping

Question 45

what does the dietary management of hepatic disease include for horses?

Answer 45

low protein, high carb, rich in branched chain amino acids - no alfalfa hay

Question 46

why avoid diazepam for a horse with hepatic encephalopathy?

Answer 46

liver metabolizes the drug - use xylazine instead