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
What is the role of lactulose in medical management?
- Promotes acidification of colonic contents, resulting in entrapment of luminla ammonia
- Decrease in colonic bacterial numbers
- Osmotic effect reduces faecal transit time
What was the MST of 27 medically managed dogs vs 99 surgically managed?
- Medical: MST 2.3yr
- Surgical: 78% still alive at 6yr
How much plasma is required to increase albumin by 1g/dL?
45ml/kg
What options are there if you cannot find the shunt vessel in surgery?
- Intraop mesenteric portovenography
- Portal catheterisation
- Intra-op Doppler ultrasound
What is a normal baseline portal pressure?
8-13cmH2O (6-10mmHg)
What is the maximum amount of contrast that can be used during mesenteric portovenography?
1200mg iodine/kg
Overdose - hypotension, arrhythmias, cardiac arrest, renal failure
List options for surgical occlusion of shunts
- Ameroid constrictor (inner casein sheath expands to decrease inner diameter by 32%
- Cellophane banding
- Hydraulic occluders
- Suture ligation (partial or complete) with 2-0 silk in dogs, polypylene in cats (can have recanalisation wtih silk)
What portal pressure measurements can help to determine amount of shunt attenuation which will be tolerated?
- Max portal pressure 17-24cmH2O (12.5-17.6mmHg)
- Maximum change of 9-10cmH2O (6.6-7.35)
- Maximum decreased in central venous pressure of 1cmH2O
- Decrease in arterial pressure of a maximum of 5mmHg or 15%
- HR should not dramatically increase
In what % of dogs does liver function return to normal after a single partial ligation?
70%
What are the broad options of treatment of an intrahepatic shunt?
- Extravascular ligation (usually of shunt or draining hepatic vein, occassionally of feeding portal branch)
- Intravascular ligation (not really one anymore)
- Intravascular coiling
What are the reported post-op complications?
- Hypogylcaemia 44%, 29% of which are refractory to dextrose
- Haemorrhage and anaemia
- Portal hypertension 2-14% with acute ligation
- Seizures and encephalopathy 3-18% dogs, 8-22% cats
What other derangement can occur with post-op hypoalbuminaemia?
Hyponatraemia - cause unknown
What are potential causes of recurrence or persistence of clinical signs post-attenuation?
- Continued flow through original shunt
- Presence of a second shunt
- Multiple acquired shunts
- Congenital PVD
- Unrelated disease
What are the reported periop mortality rates for extrahepatic PSS?
Intrahepatic?
Extrahepatic:
- Suture: 2-32%
- Ameroid: 7%
- Cellophane: 6-9%
- Good-to-excellent outcome in 78-94%
Intrahepatic:
- Suture: 6-23%
- Ameroid: 0-9%
- Cellophane: 27%
- Probability of long term survival withou recurrence 60-61% at 1yr, 55-56% at 2-4yr
What values on pre-op bloodwork may be associated with survival?
- Anaemia - poorer long-term outcome
- Increased BUN assoc with a decreased short-term survival
- Increased WBC/neutrophils assoc with decreased survival and unsuccessful long-term outome
- Higher pre-op albumin and TP assoc with better short term survive for intrahepatic PSS
- Extrahepatic ameroid: for every decreased in albumin by 1g/dL, odds of continued shunting increased 3.76 times. For every increase of albumin by 1, odds of unsuccessful outcome decreased by 0.4times
What is the perioperative mortality and prognosis in cats?
- Ameroid: 0-4.5% mortality
- Cellophane: 0-22%
- Suture: 4-20%
Good-to-excellent outcome in:
- Ameroid: 33-75%
- Cellophane: 57-80%
- Suture: 56-75%
Generalised seizures in 8-28% and central blindness in up to 44% (usually resolves within 2 months)
What % of dogs will have AV malformations in 2 lobes?
20%
What pertreatment is required prior to ligation of hepativ AV malformation?
Pretreatment with atropine or glycopyrrolate to prevent reflex bradycardia (Branham reflex)
What is the prognosis for hepatic AV malformations?
- Perioperative survival 75-91%
- Long-term outcome fair or good in 38-57%
- 75% continue to require dietary or medical management (continue to have multiple acquired shunts)
What introducing vessel is used for intrahepatic and amenable extrahepatic shunts and for AV malformation during interventistic procedures?
- PSS: Jugular vein
- AV malformations: femoral artery
What is the goal in regards to portal pressures for intravascular coiling?
- Increase the portal pressure by 7mmHg, but not higher than a final portal pressure of 15mmHg
- Coils are added until the mouth of the shunt is covered or the portal pressure is no greater than 10cmH2O (7mmHg) above baseline or a final pressure of approx 20cmH2O (15mmHg)
What kind of stent is used as a caval stent during intravascular coiling?
Laser-cut, self-explandin, nitinol stent
What medication should patients with intrahepatic shunts recieve for the rest of their lives?
Omeprazole to reduce the risk of GI ulceration
- With addition of lifelong antacids, mortality dropped from 25% to 3.2%
What can be added to cyanoacrylate glue to aid with embolisation procedures?
- 1:1 or 1:2 ratio with Ethiodol - makes mixture radioopaque and slows polymerisation
- Powdered tantalum - additional radioopacity
