Ch 96 - Hepatic Vascular Anomalies Flashcards
List the tributaries of the portal vein from caudal to cranial
- Mesenteric veins (drain the intestines and form the cranial mesenteric vein)
- Caudal mesenteric vein
- Splenic vein (with left gastric vein)
- Gastroduodenal vein (dogs)
How many hepatic veins do dogs usually have?
Which is the largest?
- 5-8 hepatic veins
- The left hepatic vein is the largest and most cranial
What embryonic vessels give rise to:
- The hepatic sinusoids
- Hepatic portion of the vena cava
- Portain vein
The vitelline vessels
What is the ductus venosus?
A venous shunt between the left umbilical vein and the cranial segment of the right vitelline vein (which become the hepatic vena cava)
What shunts most likely arise from patency of the ductus venosus?
- When is functional and structural closure expected?
- In which breed can this be delayed?
Left-sided intrahepatic PSS
- Functional closure within 2-6 days after birth
- Structural closure within 3 weeks after brith
- Delayed in Irish Wolfhounds - 23% still open at 6 days but all close by 9 days
What substances promote ductus venosus closure?
What substances slow it down?
- Promote: Endothelin, cytochrome P-450, thromboxane A2
- Slows down: Prostaglandin F1alpha, PG-E2 - cause relaxtion of the vessel, modulating the effects of endothelin
What are the three broad categories of hepatic vascular disease?
- Congenital PSS
- Disorders assoc with abnormal hepatic bloodflow or portal hypertension “primary hypoplasia of the portal vein” PVH
- Disturbances in portal outflow
What % of congenital PSS are extrahepatic?
66-75%
Where do acquired shunts most commonly enter the systemic circulation?
What are some causes of acquired shunts?
At the renal vein or the vena cava near the renal vein
Causes:
- Hepatic fibrosis
- PVH with portal hypertension
- Hepatic AV malformations
What % of dogs and cats with PVH-MVD have a concurrent congenital PSS?
- Dogs 58%
- Cats 87%
What breeds are overrepresented for PVH-MVD?
Cairn terrier, Maltese, Yorkie
How much liver function needs to be lost for hepatic encephalopathy to occur?
70%
List the various toxins inplicated in hepatic encephalopathy and their mechanisms
What usually happens to ammonia in the liver?
Converted to urea and glutamine in the urea cycle
What breeds are predisposed to exhepatic PSS?
Yorkies, Norweigan Terrier, Havanese, Maltese, Dandie Dinmont Terrier, Pugs, Min Schnauzer
What genes have been detected to have an increased expression in intrahepatic and extrahepatic shunts?
- Intra: WEE1
- Extra: VCAM1
What breed is represented for PVH-MVD accounting for 27% of cases?
Doberman
What changes may be seen on biochemistry with a PSS?
- Hypoalbuminaemia (50%)
- Reduced BUN (70%)
- Leucocytosis (poorer prognosis)
- Mild-to-mod elevation of liver enz
- Creatinine often decreased
What percentage of dogs and cats with a congenital PSS will have ammonium biurate crystalluria?
26-57% dogs
16-42% cats
What dogs may have elevated bile acid concentrations with no hepatic dysfunction?
Maltese
What is the sensitivity of the ammonia tolerance test for hepatic insufficiency?
95-100%
What is the protein C activity in normal dogs?
With PSS?
With PVH-MVD?
- Normal: 70%
- PSS: 88% have levels below 70%
- PVH-MVD: 95% have levels above 70%
What is the normal portal velocity of dogs?
15cm/s
- Icreases of variable in 53% of extrahepatic and 92% of intrahepatic PSS
What is the specificity and sensitivity of transsplenic scintigraphy fo diagnosis of congenital PSS?
What nucleotides are used?
- 100% sensitive and specific!
- Technitium-99m pertechnetate or mebrofenin
