Hepatic Vascular Anomalies

Question 1

How does a portosystemic shunt lead to liver failure?

Answer 1

Blood draining from the spleen, stomach and GI also contains trophic hormones (ex. glucagon, insulin) not just toxins. Lack of trophic hormones will lead to poor liver development, deficient protein production, altered metabolism, liver atrophy and eventually failure

Question 2

What type of congenital PSS is the most common?

Answer 2

single extra-hepatic shunt (66-75%) - mostly small breeds

Question 3

What type of shunt is more common in large breeds?

Answer 3

intra-hepatic PSS

Question 4

Which type of shunt has more severe clinical signs/ earlier onset of clinical signs?

Answer 4

intra-hepatic PSS – that’s because more blood is diverted away from the liver compared to EHPSS

Question 5

What’s the most common cause of acquired PSS?

Answer 5

portal hypertension

Question 6

What’s the most common cause of portal hypertension?

Answer 6

• hepatic fibrosis (cirrhosis)
• portal vascular hypoplasia with hypertension
  *PVH without hypertension = microscopic malformation of the hepatic vasculature – will also have other congenital abnormalities – these patients are less severely affected
• hepatic arteriovenous malformations (rare condition)

Question 7

How much liver function is lost by the time neurological abnormalities are noted?

Answer 7

70%

Question 8

What are some proposed causes of PU/PD due to PSS?

Answer 8

• poor medullary gradient due to decreased BUN
• increased renal blood flow
• increased ACTH secretion - hypercortisolism
• psychogenic

Question 9

What are the 3 body systems affected by PSS?

Answer 9

• neuro
• GI
• urinary

Question 10

What are the neurological signs associated with PSS?

Answer 10

hepatic encephalopathy
- aberrant behaviour
- ataxia
- circling
- seizure
- blind
- coma

Question 11

What are some GI signs associated with PSS?

Answer 11

• vomiting
• diarrhea
• anorexia
• pica
• GI hemorrhage – more common in large breeds with IHPSS
• ptyalism – very common in cats! 75%

Question 12

How frequent is lower urinary signs in PSS? What are the specific signs?

Answer 12

20-50% of affected patients
- hematuria
- stranguria
- pollakiuria
- urethral obstruction
- ammonium urate calculi

Question 13

Clinical signs are more commonly noted with which type of PSS?

Answer 13

Portocaval PSS - 88% vs portoazygos shunt - 58%
- shunt inserted caudal to the liver - 91%
- between liver and diaphragm - 67%

Question 14

Which type of shunt is CNS signs more common?

Answer 14

Splenocaval PSS

Question 15

Which type of shunt is urinary signs more common?

Answer 15

Right gastric > gastrosplenic v

Question 16

What type of shunt is more common in older dogs with EHPSS?

Answer 16

splenophrenic and splenoazygos shunts mor common than right gastrocaval or splenocaval

Question 17

What’s are some features of with portal vascular hypoplasia with portal hypertension?

Answer 17

• intraabdominal hypertension
• patent but small portal vein
• noncirrhotic liver

Question 18

What are some clinical signs of portal vascular hypoplasia with portal hypertension?

Answer 18

• ascites - 60%
• PU/PD
• GI upset
• HE
• weight loss

Question 19

What are some CBC abnormalities for PSS?

Answer 19

• microcystic anemia; not seen with PVH/MVD
• leukocytosis = poor prognosis
• monocytosis/ C-reactive proteins –> HE

Question 20

What are some biochem changes noted with PSS?

Answer 20

Low liver production:
- hypoglycemia
- hypocholesterolemia
- hypoalbuminemia (uncommon in cats; see low BUN/ creatinine more commonly)
- low BUN

Elevations in liver enzymes
- ALP
- ALT

Increased renal blood flow due to shunting of blood further contributes to low BUN/ creatinine

Question 21

What are some U/A abnormalities associated with PSS?

Answer 21

• low USG
• ammonium biurate crystalluria
• proteinuria (immune-mediated glomerulonephritis?)

Question 22

What’s the test of choice for evaluating liver function?

Answer 22

bile acid test
- bile acid is produced by the liver from cholesterol
- it’s than conjugated to go into the bile
- released into the duodenum to aid in lipid metabolism
- it’s then reabsorbed in the ileum (enterohepatic circulation)
The test will be evaluating the production, excretion and the enterohepatic circulation

Question 23

What are some false positive ddx for bile acid testing?

Answer 23

• Maltese! have high serum bile acids normally
• inappropriate sampling/ timing, other liver disease, steroids/ anticonvulsants, collapsed trachea, seizures, GI disease

Question 24

What other test can be done if a false negative is suspected on bile acid testing?

Answer 24

Ammonia tolerance test
- false positive if there are some enzymatic deficiencies with ammonia metabolism
- just an ammonia level test is not as sensitive as serum bile acids test

Question 25

Which coagulation pathway/ coag time would be most affected with PSS?

Answer 25

Intrinsic - leading to a prolonged PTT
- thought factor XII is also produced by the liver, PT is normal
- dogs also have thrombocytopenia but not enough to cause spontaneous bleeding
- if hypercoagulable, more likely due associated with HE

Question 26

How common is ascites with single congenital PSS?

Answer 26

rare, if noted, it’s pure transudate

Question 27

How to differentiate between PVH with or without hypertension in terms of signalment/ clinical signs?

Answer 27

PVH without hypertension
- similar clinicals signs as the typical PSS
- tend to be older, milder or non-existent signs

PVH with hypertension
- purebred dogs –> Doberman Pincher
- <4yo, >10kg
- ascites, PU/PD, GI upset, HE, and weight loss

Question 28

How does Protein C help do ddx between PSS and MVD?

Answer 28

It will be low in PSS, and >70% in 80% of dogs with MVD

Question 29

How is PSS medically managed?

Answer 29

All should be medically managed before going to surgery
Hepatoencephalopathy:
- fluids, avoid LRS
- glucose supplementation
- Lactulose/ metronidazole/ antibiotics
- mannitol
- anti-convulsant, use midazolam over diazepam –> pre-treatment with Keppra (prior to Sx) can decrease risk of post-op seizure
- milk or plant based protein
GI protectants
- H2 blockers
- sucralfate
- proton pump inhibitors
Ascites/ fibrosis (more so with NCPH or HAVM, rare with PSS)
- spironolactone (1st choice), furosemide
- prednisone, D-penicillamine, chochicine
Nutraceutical - not necessary if can be surgically/ interventional repaired
- SAMe, silymarin, vitamin E, ursodiol

Question 30

What’s the outcome with medical management alone?

Answer 30

• generally > 50% euthanized in the 1st year
• GI signs may get better
• better chance of survival in older dogs, higher BUN level
• no correlation with liver enzymes

Question 31

Which species (dog vs cat) has higher post-op complication rates (for neuro signs) for PSS?

Answer 31

cats!

Question 32

What’s the reported prognosis for hepatic vascular anomalies?

Answer 32