Hepatic Vascular Anomalies Flashcards
How does a portosystemic shunt lead to liver failure?
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
What type of congenital PSS is the most common?
single extra-hepatic shunt (66-75%) - mostly small breeds
What type of shunt is more common in large breeds?
intra-hepatic PSS
Which type of shunt has more severe clinical signs/ earlier onset of clinical signs?
intra-hepatic PSS – that’s because more blood is diverted away from the liver compared to EHPSS
What’s the most common cause of acquired PSS?
portal hypertension
What’s the most common cause of portal hypertension?
- 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)
How much liver function is lost by the time neurological abnormalities are noted?
70%
What are some proposed causes of PU/PD due to PSS?
- poor medullary gradient due to decreased BUN
- increased renal blood flow
- increased ACTH secretion - hypercortisolism
- psychogenic
What are the 3 body systems affected by PSS?
- neuro
- GI
- urinary
What are the neurological signs associated with PSS?
hepatic encephalopathy
- aberrant behaviour
- ataxia
- circling
- seizure
- blind
- coma
What are some GI signs associated with PSS?
- vomiting
- diarrhea
- anorexia
- pica
- GI hemorrhage – more common in large breeds with IHPSS
- ptyalism – very common in cats! 75%
How frequent is lower urinary signs in PSS? What are the specific signs?
20-50% of affected patients
- hematuria
- stranguria
- pollakiuria
- urethral obstruction
- ammonium urate calculi
Clinical signs are more commonly noted with which type of PSS?
Portocaval PSS - 88% vs portoazygos shunt - 58%
- shunt inserted caudal to the liver - 91%
- between liver and diaphragm - 67%
Which type of shunt is CNS signs more common?
Splenocaval PSS
Which type of shunt is urinary signs more common?
Right gastric > gastrosplenic v
What type of shunt is more common in older dogs with EHPSS?
splenophrenic and splenoazygos shunts mor common than right gastrocaval or splenocaval
What’s are some features of with portal vascular hypoplasia with portal hypertension?
- intraabdominal hypertension
- patent but small portal vein
- noncirrhotic liver
What are some clinical signs of portal vascular hypoplasia with portal hypertension?
- ascites - 60%
- PU/PD
- GI upset
- HE
- weight loss
What are some CBC abnormalities for PSS?
- microcystic anemia; not seen with PVH/MVD
- leukocytosis = poor prognosis
- monocytosis/ C-reactive proteins –> HE
What are some biochem changes noted with PSS?
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
What are some U/A abnormalities associated with PSS?
- low USG
- ammonium biurate crystalluria
- proteinuria (immune-mediated glomerulonephritis?)
What’s the test of choice for evaluating liver function?
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
What are some false positive ddx for bile acid testing?
- Maltese! have high serum bile acids normally
- inappropriate sampling/ timing, other liver disease, steroids/ anticonvulsants, collapsed trachea, seizures, GI disease
What other test can be done if a false negative is suspected on bile acid testing?
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
Which coagulation pathway/ coag time would be most affected with PSS?
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
How common is ascites with single congenital PSS?
rare, if noted, it’s pure transudate
How to differentiate between PVH with or without hypertension in terms of signalment/ clinical signs?
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
How does Protein C help do ddx between PSS and MVD?
It will be low in PSS, and >70% in 80% of dogs with MVD
How is PSS medically managed?
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
What’s the outcome with medical management alone?
- 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
Which species (dog vs cat) has higher post-op complication rates (for neuro signs) for PSS?
cats!
What’s the reported prognosis for hepatic vascular anomalies?
