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7: Digestive System > Chapter 96 Hepatic Vascular Anomalies > Flashcards

Chapter 96 Hepatic Vascular Anomalies Flashcards

1
Q

What % of hepatic blood is supplied by portal vein?

What % oxygen is supplied by portal vein?

A

80% of blood flow, 50% of oxygen

i.e. HA supplies 20% flow, 50% oxygen

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2
Q

What is the largest portal vein tributary?

A

Cranial mesenteric

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3
Q

List portal vein tributaries from caudal to cranial.

State a difference seen in cats

A

Cranial mesenteric –> Caudal mesenteric –> Splenic (to which L gastric drains) –> Gastroduodenal

No gastroduodenal vein in cats

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4
Q

Where does portal vein start to divide into right and left hepatic section, in relation to gastroduodenal vein?

A

0.5 - 1 cm cranial to gastroduodenal vein

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5
Q

In relation to hepatic portal vein branches, where are arteries and hepatic ducts usually located?

A

Ventrally (c.f. the usual veins are ventral…)

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6
Q

How many veins are there typically n the dog

A

6-8

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7
Q

Comment on hepatic vein drainange of quadrate + r medial lobe

A

Usually converge to form single terminus approx 1cm in length

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8
Q

Name the three embryonic venou systems that form portal and caval system

A

Vitelline, umbilical and cardinal

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9
Q

Briefly outline embryogenesis of portal and caval systems

A

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.

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10
Q

What is likely embryonic developmental abnormality that results in EHPSS or R/central IHPSS?

And L IHPSS

A

Persistent connections between caudal and R cranial vitelline system or malformations of hepatic sinusoids

Patent ductus venosus

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11
Q

IN relation to liver lobes, where does ductus venosus run?

A

Between L lateral and papillary process

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12
Q

In dogs, by when had ductus venosus usually closed?

A

Functional closure 6 days after birth

Structural closure after 3 weeks

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13
Q

What proportion of CPSS are extrahepatic?

A

2/3 rds

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14
Q

What are the 3 most common causes of MAPSS

A

hepatic fibrosis (cirrhosis)

PVH (PV hypoplasia) with portal hypertension

Hepatic AV malformation

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15
Q

What is idiopathic noncirrhotic portal hypertension characterised by?

A

Intra-abdominal portal hypertension + patent PV + lack of cirrhosis

N.B. This is with portal hypertension

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16
Q

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!

A

Dogs 58% had cpss

Cats 87% has cpss

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17
Q

List 3 dog breeds overrepresented fo PVH-MVD

A

Maltese, Yorkie, Cairn terrier

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18
Q

What % hepatic function has to be lost before HE

A

70%

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19
Q

List 5 toxins implicated in HE

A

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

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20
Q

What are the products of the urea cycle (matabolism of ammonia)

A

urea and glutamine

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21
Q

What % of CPSS dogs were hypercoagulable on TEG?

What factor increased risk for hypercoagulable sate?

A

43%

Presence of HE (RF x40)

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22
Q

In what breed are PDVs considered heritable

and right divisional

A

Irish Wolfhound for left divisional

Australian cattle dog for right divisional

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23
Q

What gene has been over expressed in dogs with IHPSS?

and EHPSS?

A
  • WEE1 f*or IHPSS
  • VCAM1* for EHPSS
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24
Q

What breed is over represented for PVH with non-cirrhotic portal hypertension?

A

Doberman

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25
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
26
What % of hepatic Av malformations present with ascites?
75%
27
What % of IHPSS cases have pre-op GI haemorrhage?
30%
28
What is brief pathyphysiology behind formation of urate stones in PSS
Increased renal ammonia secretion + decreased uric acid metabolism --\> ammonium urate
29
What proportion of PSS cases have urinary calculi
1/3rd
30
Classify PSS anaemia
Microcytic, normochromic, non-regenerative
31
What heam/biochem changes have been associated with HE?
Monocytosis and increased CRP
32
At what mutidtude liver enzyme increase should you consider pathology *in addition* to PSS? i..e and take a liver biopsy
if \>x4 increase
33
Where in GI tract are bile acids reabsorbed?
Ileum
34
Comment on BAST in Maltese
Haveincreased serum bile acid concentrations without other clinicopathological evidence of hepatocellular dysfunction (likely to do with spectrometry interference).
35
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 *
36
What proportion of serum ammonia is generated from GI flora in colon?
75%
37
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
38
Comment on ammonia levels in irish wolfhounds List a specific ddx in for severe hyperammoniaemia in cats without PSS List 3 other ddx for high ammonia
Have an inborn error in ammonia metabolism --\> false positives Inborn error in ammonia metabolism from a deficiency in urea cycle enzyme *ornithine transcarbamylase* *_Ddx_* * Methylmalonic acidaemia * Other urea cycle enzyme deficiencies * Urethral obstruction induced hyperammonaemia
39
In addition to BAST and ammonia, name a potential substace that can be measured for PSS dx/tx response
Hyaluronic acid (higher in PSS casesvs beagles, suspect reduced hepatic clearance)
40
What clotting factors (8 in total) do liver parenchymal cells synthesise?
I , II, V, IX, X, XI, XII, XIII
41
What is Protein C?
Vitamin-K dependent serine protease enzyme that is activated by throbin --\> anti-coag, anti-infalmmatory and anti-apoptotic effects
42
What is normal protein C activity level?
\>70%
43
List some liver histo changes seen with PSS N.B PVH-MVD histo changes share histo features What about AVM histo/
* Bile duct proliferation * Arteriolar proliferation * Intrahepatic portal tributary hypoplasia * Hepatocellular atrophy * Lipidosis * Smooth muscle hypertrophy * Increased lympahtics around central vein _AVM_ * Largely dilated portal venules * Marked arteriolar hyperplasia + muscular proliferation * Sinusoidal capillarization
44
List 3 US features of PSS
Microhepatica + reduced hepatic vasculature Renomegaly Anomalous vessel Uroliths?
45
What is normal portal flow velocity in dogs?
15 cm/s (often increased in shunts)
46
What can be used in addition to normal US evaluation of CPSS
US guided percutaneous splenic injection of agitated saline
47
What radioisotopes are used in PSS scintigraphy?
Technetium pertechnetate Technetium mebrofenin
48
What are the 2 injetion site options? Which is preferred and why?
Transsplenic or transcolonic Transsplenic preferred as better study and less radioisotope used
49
How quickly does radioisotope reach heart is PSS is present?
\<4 s
50
What is shunt fraction for PVH-MVD (if no MAPSS present) (normal vs abnormal?)?
Normal
51
What is sens/spec of transsplenic scintigraphy for dx of CPSS
100% and 100%
52
What is the half life of technetium pertechnetate?
6 hours
53
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
54
What type of CT angio is recommended for shunts?
Dual phase
55
What is the max dose of iodine (for MPV)
600-1200 mg/kg
56
How is PVH-MVD diagnosed?
Absence of shunting on advanced imaging and supportive histo
57
List 4 tx for severe HE
* Lactulose * Enema * Abx * Antiseizure * +- mannitol
58
List 3 MoA of lactulose in reducing ammonia
* Decrease GI transit time * Acidification of colonic contents --\> entrapment of ammonia as ammonium * Decreased colonic bacterial number
59
Comment of blood transfusion + HE
Whole blood preferable as pRBC contains more ammonia
60
What dietary protein % is recommended for PSS in dogs? and cats?
Dogs 20% Cats 30-35%
61
What is MSt for medically managed PSS?
1-2 years
62
Comment on clipping for IHPSS
High and wide in case of sternotomy, paracostal incision or need for cystotomy
63
List 3 methods for locating IHPSS if not visible
Intra-op US, MPV Portal catheterisation
64
What is normal portal pressure?
6-10 mmHg
65
List 4 potential complications of iodinated contrast material administration
* Hypotension * Arrythmia * Cardiac arrest * AKI
66
What is ameroid constrictor composed of?
Stainless steel sheath + casein inner ring
67
What is the % reduction in internal diameter of casein ring (of ameroid constrictor)
32% + stimulates fibrous tissue reaction in 2-5 weeks
68
What are cellophane bands made of
regenerated cellulose
69
What is hydraulic occluder made of?
Silicone + polyester cuff + vascular access port
70
What are recommendations for post-ligation portal pressures?
* Not above 17 mmHg * Max change of 7 mmHg * Max CVP decrease of 0.7 mmHg * Max ABP decrease of 5 mmHg (or 15%) * No dramatic increase in HR
71
What intra-op doppler US feature can be used to determine desired degree of shunt attenuation
Where shunt flow becomes hepatopetal
72
Broadly speaking, what are the three potential ligation sites for IHPSS Name an additional option for R divisional IHPSS
Around shunt, hepatic vein or portal vein branch Can do indirect suture pasage around R PV branch p
73
Name 5 potential post op complications following PSS ligation
* **PANS/Seizure.** Dogs 11% PANS, cats 62% pans and 20% seizure - Strickland. Tx leve, pheno, mannitol, propofol. Check for hyponatraemia (come if \<120 mEq/L * **Hypoglycaemia** 44% (can be refractory - unclear why -?give corticosteroids - NOT in ihpss - ulceration) * **Haemorrhage** (GI - unclear why) * **Portal hypertension** - tx supportive or remove suture if severe. Check for thrombus * **Recurrence of signs** - recanalization, residual shunting, PVH-MVD (most common) MAPS
74
What % of EHPSS tolerate full occlusion?
40%
75
Through which two sites can portoazygous shunts traverse the diaphragm?
Aortic or oesophageal hiatus
76
What is the reported post-op seizure rate in dogs following EHPSS ligation? And cats?
Dogs 3-18% Cats 8-22% i.e. 5-20%...
77
What suture material has been associated with shunt recanalization?
Silk
78
Central blindness has been reported in up to what % of cats?
44% (usually resolves within 2 months of surgery)
79
In which division are AVMs usually found? What % have malfomations in two lobes?
Right and central division 20% in two lobes
80
What is the nasme of the reflex that can occur during AVM closure? What physiological changes? Tx?
Branhams reflex Reduced HR, inc BP Atropine/glycopyrrolate/phentolamine
81
List 5 potential complications following sx for AVM
* Haemorrhage * Portal hypertension * Thrombus (mesenteric/portal vein) * Bradycardia * Hypotension
82
What was perio-op survivla for dogs with AVM
75-91%
83
List 3 'materials' used for abrubt embolization vs 1 for gradual
_Abrupt:_ * Cyanoacrylate glue * Vascular occluder * Stent _Gradual_ * Thrombogenic coils
84
What is the most common complication of transjugular coil embolization?
coil migation (much reduced since use of caval stents)
85
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
86
A point of note when measuring CVC for intra-vascular stent
Measure intra-abdominal during inspiration (20 cm H20), thoracic cava during expiration (i.e. measure when wiidest)
87
In what % of intravascular occlsion cases, are addition coils necessary (i.e. repeat sx)
18%
88
What are the three most common fatal complications following intravascular coil embolization
Haemorrhage (from GI bleeding) Cardiac arrest PANS/seizures --\> PTS
89
What factor was associated with GI bleedign in intravascular coil embolization cases?
Hypoalbuminaemia (\<18 g/L --\> x5 odds of bleeding)
90
What is cyanoacrylate combined with for embolization
iodized poppy seed oil +- tantalum for radiopacity
91
What arterial branches (in addition to hepatic artery) have been found to communicate with hepatic AVM
Gastroduodenal Left gastric Gastrophrenic
92
What is the most common complication of intravascular glue embolization?
Non-target embolization
93
What is reported survival rate following intravascular glue embolization for management of hepatic AVM?
100% | (vs 75 - 91% with surgery)
94
Name a no longer used surgical method for management of MAPSS
Caval banding (Also, some surgeons have ligated MAPSS after cause of portal hypertension has resolved)

7: Digestive System (12 decks)

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