Chapter 96 Hepatic Vascular Anomalies Flashcards
What % of hepatic blood is supplied by portal vein?
What % oxygen is supplied by portal vein?
80% of blood flow, 50% of oxygen
i.e. HA supplies 20% flow, 50% oxygen
What is the largest portal vein tributary?
Cranial mesenteric
List portal vein tributaries from caudal to cranial.
State a difference seen in cats
Cranial mesenteric –> Caudal mesenteric –> Splenic (to which L gastric drains) –> Gastroduodenal
No gastroduodenal vein in cats
Where does portal vein start to divide into right and left hepatic section, in relation to gastroduodenal vein?
0.5 - 1 cm cranial to gastroduodenal vein
In relation to hepatic portal vein branches, where are arteries and hepatic ducts usually located?
Ventrally (c.f. the usual veins are ventral…)
How many veins are there typically n the dog
6-8
Comment on hepatic vein drainange of quadrate + r medial lobe
Usually converge to form single terminus approx 1cm in length
Name the three embryonic venou systems that form portal and caval system
Vitelline, umbilical and cardinal
Briefly outline embryogenesis of portal and caval systems
Vitelline:
- L cranial –> atrophies
- R cranial –> hepatic CVC (with cardinal)
- Intrahepatic –> hepatic sinusoids (with umbilical)
- R + L caudal –> anastomose and atrophy in various parts –> portal vein
Umbillical:
- R + L cranial –> atrophy
- Middle –> hepatic sinusoids (with vitelline)
- R caudal –> atrophy
- L caudal –> ductus venosus
Cardinal:
- L supracardinal –> hemiazygous
- R supracardinal –> azygous
- Common cardianl –> degenerate + anastomose with with R cranial vitelline to form CVC
1, Sinus venosus;
2, superior cardinal vein;
3, inferior cardinal vein;
4, left common cardinal vein;
5, right umbilical vein;
6, liver;
7, anastomosis between the left and right omphalomesenteric vein;
8, right umbilical vein (prehepatic);
9, left umbilical vein;
10, right omphalomesenteric vein;
11, umbilical vein (unpaired);
12, inferior vena cava;
13, ductus venosus;
14, portal vein;
15, splenic vein.
What is likely embryonic developmental abnormality that results in EHPSS or R/central IHPSS?
And L IHPSS
Persistent connections between caudal and R cranial vitelline system or malformations of hepatic sinusoids
Patent ductus venosus
IN relation to liver lobes, where does ductus venosus run?
Between L lateral and papillary process
In dogs, by when had ductus venosus usually closed?
Functional closure 6 days after birth
Structural closure after 3 weeks
What proportion of CPSS are extrahepatic?
2/3 rds
What are the 3 most common causes of MAPSS
hepatic fibrosis (cirrhosis)
PVH (PV hypoplasia) with portal hypertension
Hepatic AV malformation
What is idiopathic noncirrhotic portal hypertension characterised by?
Intra-abdominal portal hypertension + patent PV + lack of cirrhosis
N.B. This is with portal hypertension
What proportion of Portal Vein Hypoplasia - Microvascular dysplasia (PVH-MVD) cases have CPSS:
In dogs?
and cats?
NB. this is separate entity from idiopathic noncirrhotic portal hypertension. The difference if that PVH-MVD does not have portal hypertension, whereas idiopathic non-cirrhotic portal hypertension does!
Dogs 58% had cpss
Cats 87% has cpss
List 3 dog breeds overrepresented fo PVH-MVD
Maltese, Yorkie, Cairn terrier
What % hepatic function has to be lost before HE
70%
List 5 toxins implicated in HE
Ammonia
Aromatic amino acids
Bile acids
Decreased alpha-ketoglutaramate
Benzodiazepines (endogenous)
False neurotransmitters
Tyrosien –> octopamine
Methionine –> mercaptans
Gaba
Glutamine
Phenol
Short chain fatty acids
Tryptophan
What are the products of the urea cycle (matabolism of ammonia)
urea and glutamine
What % of CPSS dogs were hypercoagulable on TEG?
What factor increased risk for hypercoagulable sate?
43%
Presence of HE (RF x40)
In what breed are PDVs considered heritable
and right divisional
Irish Wolfhound for left divisional
Australian cattle dog for right divisional
What gene has been over expressed in dogs with IHPSS?
and EHPSS?
- WEE1 f*or IHPSS
- VCAM1* for EHPSS
What breed is over represented for PVH with non-cirrhotic portal hypertension?
Doberman
List proposed mechanisms for PUPD in PSS
- Low urea –> poor medullary concentration gradient
- Increased renal blood flow (increased GFR and renal volume in 81% of dogs with PSS)
- Increased ACTH
- Psychogenic polydipsia from HE
What % of hepatic Av malformations present with ascites?
75%
What % of IHPSS cases have pre-op GI haemorrhage?
30%
What is brief pathyphysiology behind formation of urate stones in PSS
Increased renal ammonia secretion + decreased uric acid metabolism –> ammonium urate
What proportion of PSS cases have urinary calculi
1/3rd
Classify PSS anaemia
Microcytic, normochromic, non-regenerative
What heam/biochem changes have been associated with HE?
Monocytosis and increased CRP
At what mutidtude liver enzyme increase should you consider pathology in addition to PSS? i..e and take a liver biopsy
if >x4 increase
Where in GI tract are bile acids reabsorbed?
Ileum
Comment on BAST in Maltese
Haveincreased serum bile acid concentrations without other clinicopathological evidence of hepatocellular dysfunction (likely to do with spectrometry interference).
List ddx for false positive BAST
And false negative
Ddx high BAST
- Cholestasis
- Other hepatobiliary disease
- Glococorticoids
- Antiseizure medications
- Inappropriate sampel timing
- Spontaneous GB contraction (–> pre-prendial higher)
Ddx low BAST
- Delayed transit time/gastric emptying
- Inadequate GB contraction/food intake
- Malabsorbtion/maldigestion
*
What proportion of serum ammonia is generated from GI flora in colon?
75%
What test can be run in animal with normal baseline ammonia and suspected liver disease?
Briefly outline how its performed
List a contraindication
Ammonia tolerance test
Take serum ammonia level
Give ammonium chloride (100 mg/kg) po or pr.
Repeat serum ammonia 30 mins after administration
Contraindicated if baseline ammonia already high
Describe the findings in the following scintigraphy series
Transsplenic scintigraphy.
A, Extrahepatic portocaval shunt in a Labrador Retriever. Blood flow from the spleen enters the heart at its caudodorsal aspect.
B, Portoazygos shunt in a Yorkshire Terrier. Blood flow from the spleen enters the heart at its craniodorsal aspect.
C, Multiple acquired shunts in a Chihuahua. Blood flow travels caudally from the spleen before entering the caudal vena cava.
N.B. Hetpatofugal flow usually indicative of MAPSS, but can also have hepatofugal flow in colonocaval shunts
Describe what is happenig in images:
Percutaneous transjugular coil embolization of a right divisional intrahepatic portosystemic shunt (PSS). The animal is placed in dorsal recumbency with the head to the left and the tail to the right of the image.
A, A guide wire (yellow arrow) is placed from the jugular vein through the cranial vena cava, right atrium, and caudal vena cava (CdVC) and extending down the CdVC. A catheter is placed similarly but selected to be in the shunting vessel, ending in the portal vein (red arrow); it extends from the jugular vein, through the cranial and CdVC, and traversing the right hepatic vein, the PSS and into the portal vein.
B, An angiogram being performed under digital subtraction angiography fluoroscopy. Contrast material is in both the CdVC and portosystemic shunting vessel. The shunt catheter (red arrow) extends into the portal vein. The mouth of the shunt is identified (black triangle). Using a marker catheter (yellow arrow), magnification is adjusted for; the vena cava can be accurately measured for appropriate selection of stent size.
C, Over a guide wire, the ensheathed stent (red asterisk) is advanced into the CdVC to cover the entire mouth of the shunt that was previously determined in B.
D, The stent is then deployed in the selected location with each end (red asterisks) confirmed to cover the shunt.
E, The mouth of the shunt is again selected with a catheter (blue triangle).
F, Another angiogram is done using contrast to confirm that the stent is covering the entire mouth of the shunt.
G, Through the catheter, thrombogenic coils are placed into shunting vessel (arrow) upstream of stent.
H, Final angiogram under digital subtraction, final portal pressures
