Hepatic Disease in Horses

Question 1

when is function impaired in hepatic mass loss?

Answer 1

80% of hepatic mass lost

Question 2

why can liver disease cause anorexia?

Answer 2

accumulation of waste products suppressing appetite centers

Question 3

what are the three main pathways for icterus in horses?

Answer 3

anorexia-associated
hemolysis
cholestasis (liver disease)

Question 4

what is hepatic encephalopathy?

Answer 4

abnormal mental status that accompanies severe hepatic insufficiency

Question 5

what is hepatic photosensitization due to?

Answer 5

increased phylloerythrin in skin

Question 6

what are the two differential diagnoses for photosensitization?

Answer 6

healthy horse consuming photosensitizing plants- eating normally
liver disease- anorexia and weight loss too

Question 7

which clotting factors does the liver normally synthesize?

Answer 7

fibrinogen
factors II, VII, IX, X, protein C

Question 8

where is lactulose metabolized?

Answer 8

colon

Question 9

why does unconjugated bilirubin rise in decreased liver function?

Answer 9

decreased hepatic uptake

Question 10

what are normal bile acid levels?

Answer 10

<11 micromol/L

Question 11

what should you assess the liver for with ultrasonography?

Answer 11

right and left liver
size, shape, position, echogenicity

Question 12

what information can liver biopsy give?

Answer 12

diagnostic
prognostic

Question 13

what is the cause of the majority of liver diseases in horses?

Answer 13

bacterial

Question 14

what causes tyzzer’s disease?

Answer 14

Clostridium piliforme

Question 15

what is bacterial hepatitis/cholangiohepatitis diagnosed based on?

Answer 15

histopathology and culture of liver biopsy samples

Question 16

what type of disease is parasitic hepatitis usually?

Answer 16

focal disease only

Question 17

what can cause acute biliary obstruction?

Answer 17

large colon torsion
torsion of liver lobe (extremely rare)
secondary to cholelithiasis

Question 18

what causes hepatic lipidosis?

Answer 18

negative energy balance
lipid accumulation in blood (hyperlipidemia)
lipid infiltration of liver, kidneys, intestine

Question 19

what is the treatment of theiler’s disease/equine parvovirus-hepatitis?

Answer 19

supportive care

Question 20

what does pyrrolizidine alkaloid toxicity cause?

Answer 20

chronic megalocytic hepatotoxicity
clinical signs 4 weeks-12 months later: hepatic failure

Question 21

what is seen on biopsy of pyrrolizidine alkaloid toxicity?

Answer 21

classic triad:
megalocytosis
biliary hyperplasia
bridging fibrosis

Question 22

when do you see clinical signs with clover poisoning?

Answer 22

2 weeks after consumption
diet at least 20% clover

Question 23

what is the treatment for cholelithiasis?

Answer 23

long-term antibiotics

Question 24

what can occur in older horses?

Answer 24

atrophy of right liver lobe

Question 25

what causes yellowing of sclera from grazing on green pasture?

Answer 25

xanthophylls in grass

Question 26

what are the three main pathophysiological mechanisms of hepatic encephalopathy?

Answer 26

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

Question 27

what can be abnormal in clotting in liver disease?

Answer 27

prothrombin time
activated partial thromboplastin time

Question 28

how can we treat hepatic insufficiency?

Answer 28

supportive therapies
IV fluids
IV dextrose/glucose
anti-inflammatory drugs
milk thistle
S-adenosylmethionine

Question 29

why would we give lactulose for hepatic encephalopathy?

Answer 29

decreases ammonia absorption

Question 30

how does lactulose decrease ammonia absorption?

Answer 30

metabolized to volatile fatty acids in colon: lowers pH
ammonia converted to NH4+ and trapped in gut lumen

Question 31

what are some tests for liver function?

Answer 31

unconjugated and conjugated bilirubin
bile acids
ALP

Question 32

what are some tests for liver damage?

Answer 32

AST
GGT
SDH
LDH (-5)
GLDH

Question 33

bile acids above _________ are highly specific for liver disease/dysfunction

Answer 33

20 micromol/L

Question 34

what are the negatives of doing a liver biopsy?

Answer 34

hemorrhage risk
often histopath does not give definitive diagnosis

Question 35

where is a liver biopsy done?

Answer 35

right 12-14 intercostal spaces
ultrasound guided

Question 36

what are some chronic liver diseases?

Answer 36

pyrrolizidine alkaloid toxicity
clover poisoning
chronic active hepatitis
cholelithiasis
abscess
neoplasia

Question 37

what are some acute liver diseases?

Answer 37

bacterial
parasites
toxins
acute biliary obstruction
hepatic lipidosis
viral diseases

Question 38

who gets tyzzer’s disease?

Answer 38

foals 7-42 days

Question 39

what does tyzzer’s disease cause?

Answer 39

acute hepatic failure
not contagious

Question 40

what usually causes bacterial hepatitis/cholangiohepatitis?

Answer 40

ascending infection
usually common enteric organisms

Question 41

what can cause parasitic hepatitis?

Answer 41

Parascaris equorum
Strongylus edentatus or equinus
S. vulgaris
Echinococcus granulosa
liver fluke

Question 42

what are some hepatic viral diseases?

Answer 42

non-primate hepacivirus
equine parvovirus-hepatitis: theiler’s
equine pegivirus

Question 43

what are the clinical signs of theiler’s disease/equine parvovirus-hepatitis?

Answer 43

acute to subacute hepatic failure
2-7 days

Question 44

what is the prognosis of theiler’s disease?

Answer 44

guarded

Question 45

what is seen on histopathology with theiler’s disease?

Answer 45

widespread centrilobular to midzonal hepatocellular necrosis with hemorrhage, lymphocytic/plasmocytic infiltration

Question 46

what is cholelithiasis associated with?

Answer 46

bacterial infection