Hepatic vascular anomalies

Question 1

In a study by Freund 2020 in Vet Surg, did the application of a thin film to the external iliac vein of cats result in consistent occlusion by 8-weeks?

Answer 1

No - complete occlusion only in 1/6 cats despite the presence of granulomatous inflammation. Supports the theory that residual shunting may occur in cats after cellophane banding.

Question 2

According to Matiasovic 2020 in Vet Surg, did thin film banding or ameroid constrictor for portosystemic shunt attenuation in dogs result in a higher rate of persistent shunting?

Answer 2

Thin film banding (29%) of dogs compared to 0% for ameroid constrictors.

Compare to the study by Otomo 2020 in Vet Surg which reported no difference in clinical outcomes between groups.

Question 3

According to Mullins 2020 in Vet Surg, what was the 30 day survival in dogs suffering post-operative seizures following PSS attenuation? What were factors positively associated with short term survival?

Answer 3

32% of patients survived to 30 days.

Factors positively associated with survival included having preoperative seizures and development of focal PAS only.

Question 4

In a study by Strickland 2020 in Vet Surg, what was the rate of PANS in cats treated for single congenital PSS? Was the use of perioperative levetiracetam associated with a decreased risk of PANS?

Answer 4

62% (5/31 did not survive to discharge)

Levetiracetam did not decrease the risk.

Question 5

In a review of PANS by Mullins 2021 in Vet Surg what was the reported rate of PANS amongst all studies? What were 4 potential risk factors for development of PANS?

Answer 5

Reported rate of 2-27% (PAS rate of 0-18%).

Identified risk factors for development of PANS include preoperative hepatic encephalopathy, increasing age, certain breeds, and extrahepatic shunt morphology.

Question 6

What are two blood tests suggested by Devriendt 2022 in Vet Surg that may be useful in determining complete EHPSS closure after treatment?

Answer 6

Serum hyaluronic acid and lidocaine/monoethylglycylxylidide test.

These can also be combined with fasted ammonia and serum bile acids for improved sensitivity and specificity.

Question 7

In a study by Sunlight 2022 in Vet Surg, what post-operative biochemical changes were associated with excellent clinical outcomes following percutaneous transvenous coil embolization of IHPSS?

Answer 7

Increased protein-C,
Also, HCT, MCV, ALB, BUN

Question 8

In a review by Mullins 2023 in Vet Surg, what are the reported rates of PANS and post-attenuation seizures in cats? What are two risk factors that have been identified for development of PANS?

Answer 8

Incidence of PANS is 14.3-62%, and postattenuation seizures is 0-32%.

Risk factors include post-operative osmolality, and lower grades of intraoperative postocclusion mesenteric portovenography.

Question 9

In a study by Janas 2024 in Vet Surg, what 5 perioperative complications were reported following EHPSS attenuation with ameroid constrictors in 5 cats? What was the long term clinical outcome?

Answer 9

Perioperative complications reported including blindness, seizures, ascites, head pressing, and death.

The long term outcome was good to excellent in 16/18 cats.

Question 10

In a study by Spies 2024 in Vet Surg, what were the two most common shunt EHPSS shunt configurations in dogs >15kg? What was the percentage of short term complications and shunt related deaths?

Answer 10

Portocaval and splenocaval were the most common morphologies (Golden retrievers most common breed).

Short term complications occurred in 36% of dogs and 7% had shunt related deaths. Portal vein hypoplasia was observed frequently on imaging.

Question 11

In a study by Carrera 2022 in JAVMA, in dogs with PANS that survived for >30 days what percentage of neurologic signs present at the time of discharge ultimately resolved? What percentage of dogs survived >6 months? What percentage of dogs with initial seizures suffered recurrence?

Answer 11

67% of neurologic signs present at the time of discharge resolved.

90% of dogs survived >6 months.

50% of dogs with initial seizures had recurrence.

Question 12

In a study by White 2020 in JSAP, at the level of the omental foramen what was the final vessel that communicated with the caudal vena cava in all cases of canine EHPSS? Label an image of the portal vasculature.

Answer 12

Regardless of the tributary vessels, the left gastric vein was the final vessel that communicated with the caudal vena cava in all cases.

Question 13

In a study by Glenn 2022 in JSAP, what material was used for EHPSS occlusion in dogs as an alternative to cellophane? What was the mortality rate and rate of recurrence? What was the overall percentage of patients who had a good outcome?

Answer 13

Polyethylene band from the packaging of a urinary catheter was used.

Mortality rate was 7%, and recurrence rate was 17%.

Excellent or good outcomes were achieved in 82% of dogs.

Question 14

In a study by Wilson 2021 in VRU, what imaging technique was used for anatomically characterizing canine hepatic vascular anomalies with similar results as CTA?

Answer 14

Ferumoxytol (a long acting MRI contrast agent) enhanced MR angiography.

Question 15

In a study by Humphreys 2024 in VRU, what imaging finding was consistently identified in dogs with EHPSS?

Answer 15

A significant increase in the hepatic artery to aorta ratio. An increase in the hepatic artery is thought to be secondary to the arterial buffer response of the liver, which sees an increase in hepatic arterial flow in response to reduced portal flow.

Question 16

In a study by Economu 2022 in JFMS, what was the most common shunt morphology in cats with IHPSS? What percentage of cats developed PANS after surgical attenuation? What percentage of cats had an excellent outcome post-operative?

Answer 16

Left divisional was most common. Acute attenuation was possible in 3 cats, whereas 8 underwent partial attenuation (of which 50% required a second surgery for complete suture ligation).

PANS developed in 50% of cats (17% died or were euthanized because of PANS).

Excellent outcomes were achieved in 63% of cats.

Question 17

In a study by Serrano 2022 in JVIM, which of the following medical management options resulted in the greatest improvements in clinical signs for dogs with EHPSS?
1) Hepatic diet
2) Hepatic diet + lactulose
3) Hepatic diet + metronidazole

Answer 17

Hepatic diet and lactulose. Addition of metronidazole did not result in a further reduction in clinical signs.

Medical management was associated with reductions in fasting ammonia.

Question 18

What is the largest portal vein tributary?

Answer 18

Cranial mesenteric vein

Question 19

Are branches of the hepatic artery and bile ducts typically located on the ventral or dorsal surface of the portal vein?

Answer 19

Ventral

Question 20

Describe the termination of the hepatic veins onto the vena cava?

Answer 20

The right lateral and caudate hepatic veins are completely surrounded by hepatic parenchyma.

Question 21

Left-sided intrahepatic shunts most likely result from patency of which embryonic structure?

Answer 21

Ductus venosus (normally closes within 2-6 days after birth).

Question 22

Portocaval and portoazygous shunts are inappropriate connections between which embryologic systems?

Answer 22

Cardinal and vitelline.

Question 23

What is another term for portal vein hypoplasia (PVH) without portal hypertension?

Answer 23

Microvascular dysplasia.

Question 24

In dogs and cats, what percentage of congenital single PSS are extrahepatic?

Answer 24

66-75%

Extrahepatic shunts are more common in small breed dogs, intrahepatic in large breed dogs.

Question 25

What are the most common causes of acquired extrahepatic shunting?

Answer 25

Hepatic fibrosis (cirrhosis), PVH with portal hypertension (congenital noncirrhotic portal hypertension), and hepatic arteriovenous malformations.

Question 26

What is the most common location for acquired extrahepatic shunts?

Answer 26

Usually multiple, tortuous vessels connecting a portal tributary directly to the renal vein or caudal vena cava near the kidney.

Question 27

Name the following EHPSS.

Answer 27

Question 28

What percentage of dogs with macroscopic congenital PSS have PVH-MVD?

Answer 28

58% of dogs, and 87% of cats.

Question 29

What are the clinical signs for patients with PVH-MVD without PSS?

Answer 29

Often similar to PSS but may be less severe, present later in life and better long term prognosis with medical management alone.

Question 30

Which dog breeds are predisposed to PVH-MVD?

Answer 30

Cairn Terrier, Maltese, Yorkshire Terrier.

Question 31

What is hepatic arteriovenous malformation (AVM)?

Answer 31

Direct communication of the hepatic artery to the portal system through tens to hundreds of shunting vessels. Results in arterialization of the portal vein, hepatofugal blood flow, and numerous acquired EHPSS formation.

Question 32

How much liver function has to be lost for hepatic encephalopathy to occur?

Answer 32

>70%

Question 33

What is the effect of increased levels of ammonia with PSS?

Answer 33

Ammonia is excitotoxic and is associated with an increased release of glutamate, the major excitatory neurotransmittor of the brain. With chronicity inhibitory factors such as GABA and endogenous benzodiazepines may surpass this excitatory stimulus and create signs more suggestive of coma or CNS depression.

Question 34

Where is ammonia produced?

Answer 34

Produced by normal GI flora. Normally converted to urea and glutamine in the liver by the urea cycle.

Question 35

What percentage of dogs with PSS had a hypercoaguable state?

Answer 35

43%

Question 36

What dog breed is at highest risk for EHPSS?

Answer 36

Yorkshire terrier (36 x the risk of all other breeds combined).

Question 37

In what dog breed are left-divisional intra-hepatic PSS considered heritable?

Answer 37

Irish wolfhounds and Australian cattle dogs. Male dogs in Australia overepresented with right divisional PSS.

Question 38

What are some potential causes of polyuria in dogs with PSS?

Answer 38

Poor medullary concentrating gradient due to low BUN, increased renal blood flow, increased ACTH secretion with associated hypercortisolism, psychogenic polydipsia from hepatic encephalopathy.

Question 39

What percentage of dogs with hepatic AVM have abdominal effusion?

Answer 39

75%. Also may occur with acquired shunting, or with severe hypoalbuminemia in cases of PSS.

Question 40

What are some common clinical signs associated with PSS in dogs and cats?

Answer 40

CNS signs, GI signs (30% of dogs, less common in cats), GI hemorrhage in 30% of dogs with IHPSS, lower urinary tract signs, urinary tract calculi (36%), copper-coloured irises (particularly in cats), ptyalism very common in cats (75%).

Question 41

What is the mechanism behind formation of ammonium urate urolithiasis?

Answer 41

Decreased production of urea, increased excretion of ammonia by the kidneys, decreased uric acid metabolism.

Question 42

Which specific types of shunt morphology tend to have less severe clinical signs?

Answer 42

Portoazygous and portophrenic, due to possible compression by the stomach and diaphragm. Shunts that insert caudal to the liver more likely to cause clinical signs than shunts inserting caudal to the diaphragm.

Question 43

What clinical signs are common in patients with hepatic AVM?

Answer 43

Abdominal effusion (75%), GI signs often severe, hepatic encephalopathy reported less frequently than with PSS.

Question 44

What are some common clinicopathologic findings in patients with PSS?

Answer 44

CBC: Microcytic normochromic nonregenerative anemia (60% dogs, 30% cats; generally not seen with PVH-MVD), target cells in dogs and poikilocytes in cats, leukocytosis. Biochem: hypoalbuminemia (50%, uncommon in cats), reduced BUN (70%), hypocholesterolemia, hypoglycemia. Increased ALP and ALT (ALP > ALT in patients with PSS, and both values rarely >4x normal, ALT might be higher if acquired shunting is present). Urinalysis: decreased USG, ammonium biurate crystalluria, proteinuria (secondary to immune mediated glomerulonephritis secondary to antigens reaching the kidneys that would normally be removed by the liver).

Question 45

What percentage of dogs with PSS have increased renal blood flow and GFR?

Answer 45

81%

Question 46

What liver function tests are recommended for assessment of suspected PSS?

Answer 46

1. Bile acid testing (12-hour fasting and 2-hour postprandial). 2. Fasted ammonia (only positive in 62-88% of animals with PSS) +/- ammonia tolerance test.

Question 47

What might cause false/negative positive bile acid test results when assessing PSS?

Answer 47

Positive: Maltese dogs, inappropriate timing, other hepatobiliary disease, cholestasis, glucocorticoid or anticonvulsant therapy, tracheal collapse, seizures, GI disease. Negative: lack of gallbladder contraction, delayed intestinal absorption due to prolonged transit time, inadequate food intake, delayed gastric emptying, malabsorption, maldigestion.

Question 48

Which dog breed might have false positive results for fasting ammonia testing?

Answer 48

Irish wolfhound puppies (inborn error of ammonia metabolism).

Question 49

What is the sensitivity of ammonia tolerance testing for PSS? When should this not be performed?

Answer 49

95-100%. Should not be performed in patients with preexisting hepatic encephalopathy.

Question 50

What two hepatic vascular anomalies can protein C be useful in differentiating between?

Answer 50

Normal dogs: >70% protein C activity PSS: <70% PVH-MVD: >70% Deficiencies in protein can also be caused by increased consumption (DIC, thrombosis, surgery), renal disease and malignancy.

Question 51

What radiographic findings are suggestive of PSS?

Answer 51

Microhepatica (60-100% dogs, 50% cats), bilateral renomegaly. Calculi may also be seen, but can be radiolucent.

Question 52

What imaging techniques can be used for definitive PSS diagnosis?

Answer 52

1. Ultrasound: more accurate at detecting IHPSS than EHPSS. Changes in flow direction (AVM) or velocity (IHPSS>EHPSS) may also be observed. 2. Scintigraphy: transcolonic or transplenic injection of technetium pertechnetate. Shunt fraction 70-95% in dogs with PSS (normal in PVH-MVD). 3. CT angiography. 4. MRI 5. Portovenography: operative mesenteric portovenography. Best performed in left lateral recumbency (100% sensitivity). May not detect PSS if transsplenic injection is used and shunt is upstream (although may opacify due to hepatofugal flow). Splenic injection can result in life threatening hemorrhage if AVM present.

Question 53

What hepatic vascular anomalies are depicted by the scintigraphy images?

Answer 53

Question 54

What diagnostic findings would indicate PVH-MVD in the absence of PSS?

Answer 54

Elevated bile acids, imaging negative for PSS, hepatic biopsy results consistent with PVH-MVD.

Question 55

Describe the medical management of portosystemic shunts.

Answer 55

Question 56

Why is it recommended to avoid use of diazepam in patients with hepatic encephalopathy?

Answer 56

Endogenous benzodiazepines and GABA may contribute to hepatic encephalopathy. Benzodiazepine antagonists (flumazenil) have been used to reverse hepatic encephalopathy induced comas.

Question 57

What are the effects of lactulose in the medical management of PSS?

Answer 57

It is metabolized by colonic bacteria to organic acids. This results in acidification of the colonic contents, trapping of ammonia, and reduction in bacterial numbers. Its osmotic effect also produces catharsis, reducing fecal transit time and bacterial exposure to minimize ammonia production and absorption.

Question 58

What is the median survival time for dogs with PSS treated with medical management alone?

Answer 58

9.9 months. In another study MST was 2.3 years for medically managed dogs, and wasn't reached for surgically managed dogs. Prognosis was better in dogs that were older at the time of diagnosis, had extrahepatic PSS, or higher BUN concentrations.

Question 59

What are options for surgical shunt occlusion?

Answer 59

Ligation, ameroid constrictor, cellophane banding, hydraulic occluder.

Question 60

What are methods of shunt localization during surgery?

Answer 60

Direct visualization, ultrasonography, operative mesenteric portography, evaluation of portal pressure changes. Portal catheter placement through a purse string may also facilitate palpation of IHPSS location.

Question 61

When would shunt attenuation be contraindicated?

Answer 61

Agenesis or atresia of the portal vein.

Question 62

What is shown in the attached imagee?

Answer 62

Multiple acquired shunts. Normally identified near the kidney in the intestinal mesentery.

Question 63

How can intraoperative portal pressures be measured?

Answer 63

Insertion of a catheter in a jejunal or splenic vein, or the portal vein.

Question 64

What is normal baseline portal pressure?

Answer 64

8-13 cmH2O (6-10 mmHg)

Question 65

What is the maximum dose of iodine that can be administered for mesenteric portography?

Answer 65

1200 mg of iodine per kg. Overdose can cause hypotension, arrhythmias, cardiac arrest, and renal failure.

Question 66

Can the use of intraoperative mesenteric portography help to predict outcome in dogs and cats undergoing PSS attenuation?

Answer 66

Cats: increased aborization following attenuation less likely to have neurologic complications and better clinical response to surgery. Dogs: increased pre-ligation arborization associated with ability to completely occlude the shunt, but not related to clinical response. Deceased pre-ligation arborization associated with increased post-operative complications.

Question 67

How much does swelling of the casein substance in an ameroid ring constrictor reduce the internal diameter?

Answer 67

32%. Remainder of closure of vessel due to fibrous tissue reaction.

Question 68

How long does shunt attenuation take with ameroid constrictors and hydraulic occluders?

Answer 68

Ameroid constrictor: 2-5 weeks, most rapid during first 3-14 days. Hydraulic occluder: 6-8 weeks (small amount of sterile saline injected every 2 weeks). Closure does not depend on fibrous tissue formation.

Question 69

Why might use of cellophane banding not be ideal for use in cats with PSS?

Answer 69

Persistent flow has been reported in some cats, suspected secondary to reduced inflammatory response in this species.

Question 70

What material should be used for suture ligation of PSS in cats?

Answer 70

Nonabsorbable synthetic monofilament suture due to the risk of recanalization in this species. Silk may be preferred in dogs.

Question 71

What are visual intraoperative signs of portal hypertension?

Answer 71

Pallor or cyanosis of the intestines, increased peristalsis, cyanosis or edema of the pancreas, increased mesenteric vascular pulsations.

Question 72

What are recommended post-ligation portal pressures for complete suture attenuation of PSS?

Answer 72

1. Maximum portal pressure of 17-24 cmH20 (13-18 mmHg). 2. Maximum change in portal pressure of 9-10 cmH20 (7mmHg). 3. Maximum decreased in CVP of 1cmH20. 4. Maximum decrease in arterial pressure of 5 mmHg or 15% or less. 5. Heart rate should not increase dramatically.

Question 73

How can doppler ultrasonography be used to help determine the degree of attenuation of a PSS intraoperative?

Answer 73

Degree of attenuation should be limited to a point where shunt flow becomes hepatopetal and cranial portal vein flow remains hepatopetal.

Question 74

In what order are medications discontinued post-operatively for PSS?

Answer 74

Antibiotics, lactulose, then diet. Typically weaned over 2-3 months after surgery, based on bile acids, biochem and clinical signs.

Question 75

Is normalization of bile acids following surgical correction of PSS associated with long-term outcome?

Answer 75

No, may remain elevated. Clinical outcome unchanged so long as clinical signs and biochemical parameters improve.

Question 76

What are some complications associated with correction of PSS?

Answer 76

Hypoglycema (44% of dogs, 30% refractory to dextrose): treated with boluses of 25-50% dextrose, oral alimentation +/- glucocorticoids (EHPSS only). Hemorrhage and anemia: surgical blood loss, sequestration/large fluid loads, coagulation deficits, GI loss. Portal hypertension (2-14% of patients undergoing acute shunt ligation): treated with oxygen, warmth, IV fluids, hetastarch, GI protectants, analgesics, antimicrobials +/- FFP, whole blood. Ligature removal may be required. In mild cases treatment with spirinolactone may be adequate for management of ascites. Seizures and encephalopathy (3-18% of dogs, 8-22% of cats): treated with boluses of midazolam or diazepam +/- levetiracetam, phenobarbital +/- propofol CRI. Mannitol to reduce intracranial swelling. Correct electrolyte abnormalities. In cases of severe hyponatremia causing seizures (<120 mEq/L), correct deficit slowly (<1 mEq/h). Recurrence of clinical signs: continued flow, second shunt, acquired shunting, PVC +/- portal hypertension, unrelated disease.

Question 77

What are clinical signs of portal hypertension following shunt attenuation?

Answer 77

Hypovolemic shock, abdominal pain, abdominal distension, diarrhea, vomiting, ascites. Can be exacerbated by overhydration, bandaging, vocalization, defecation, large meals.

Question 78

What are potential causes of post-operative PANS following PSS attenuation?

Answer 78

Decreases in endogenous inhibitor central nervous system benzodiazepines agonist levels, imbalances in excitatory and inhibitory neurotransmitters.

Question 79

What is the perioperative mortality rate of dogs undergoing PSS correction?

Answer 79

Suture ligation: 2-32% Ameroid: 7% Cellophane: 6-9% Mortality higher for IHPSS (~10-20%).

Question 80

What is the long term outcome for patients undergoing PSS correction?

Answer 80

Generally good. Better for patients with complete shunt attenuation. Outcome more variable in patients undergoing surgery for IHPSS, although resolution of clinical signs are common despite persistent shunting.

Question 81

What are some factors that influence the outcome of dogs undergoing PSS correction?

Answer 81

Large breed dogs more likely to have recurrence of clinical signs (although dogs >10kg had more favourable short term outcome for IHPSS attenuation). Anemia associated with poorer long term outcome, increased BUN associated with decrease in short term survival with IHPSS. Increased survival with greater preoperative albumin and total protein (IHPSS), risk of shunting increased with decreasing albumin (EHPSS; decrease of 1 g/dL = 4 x increase in odds of continued shunting). Dogs with greater liver size more likely to tolerate acute shunt occlusion. Animals tolerating acute shunt ligation normally have a better outcome.

Question 82

What is the complication rate for cats undergoing PSS attenuation?

Answer 82

75%, most frequently PANS (seizures in 28%, blindness 44%). Blindness normally resolves within 2 months. Mortality rates: Ameroid = 0-4.5% Cellophane: 0-22% Suture ligation: 4-20%

Question 83

In which liver lobes are AVM normally found?

Answer 83

Right or central divisional. Multiple lobes affected in 20% of dogs.

Question 84

What is the treatment for AVM?

Answer 84

Surgical resection of the affected lobe. Can be useful to temporarily occlude the nutrient artery prior to ligation to confirm that it is the source of the fistula (should see a rise in portal pressure).

Question 85

What reflex might be observed following ligation of an AVM?

Answer 85

Branham reflex (treated with atropine or glycopyrrolate).

Question 86

What percentage of dogs surgically treated for AVM require ongoing dietary or medical management post-operative?

Answer 86

75%

Question 87

Which vessels is used for the approach for transvenous coil embolization of IHPSS in dogs?

Answer 87

Jugular.

Question 88

What is the most common complication following transvenous coil embolization of IHPSS?

Answer 88

Coil migration (reduced with the use of caval stenting). Portal hypertension is rare.

Question 89

When measuring the venal cava for stent placement during transvenous PSS coil embolization, should measurements be obtained under positive pressure ventilation?

Answer 89

Intraabdominal measurements should be obtained under 20 cmH20 of positive pressure ventilation, thoracic measurements should be obtained without.

Question 90

What portal pressure measurements are the end-goal of tranvenous coil embolization for PSS?

Answer 90

1. Increase in portal pressure of 10 cmH20 (7 mmHg). 2. Final portal pressure of 20 cmH20 (15 mmHg). Note: coiling should only be performed if initial caval to portal pressure gradient is less than <6-7 mmHg.

Question 91

Addition of coils is required in what percentage of cases following transvenous coil embolization for PSS?

Answer 91

18% 3% of shunts can undergo complete occlusion (portal perfusion is well developed on angiography).

Question 92

What is the complication rate following transvenous coil embolization for PSS?

Answer 92

15% complication rate: coil migration, bleeding from the jugular catheter, post-operative neurologic activity (6%), GI bleeding/signs (increased risk with decreasing albumin concentrations). Portal hypertension not typically seen.

Question 93

What is the perioperative mortality rate following transvenous coil embolization for PSS?

Answer 93

5%. Normally due to GI bleeding, cardiac arrest, or continued neurologic signs.

Question 94

What interventional radiology technique has been described for the treatment of hepatic AVM?

Answer 94

Cyanoacrylate glue embolization. Typically performed via the femoral artery.

Question 95

What is the outcome following cyanoacrylate embolization of hepatic AVM?

Answer 95

Generally good although most dogs require lifelong medical management due to acquired shunting. Nontarget embolization is the main complication, but is rarely clinically significant.