hepatic vascular anomalies (Ganjei) Flashcards
The gallbladder sits between what lobes in dog/cat?
Right medial and the quadrate lobes
Describe the role of the hepatic artery in the liver
supplies 20-25% of blood volume, and 50% of O2
arises from celiac artery
Describe the role of the portal vein in the liver
Supplies 75-80% of blood volume to liver and 50% of O2
- portal vein drains blood from various abdominal organs (SI, stomach, spleen, colon, pancreas, rectum)
Describe flow of blood starting with portal vein and ending with the heart
portal vein -> liver detoxifies blood -> detoxified blood in central vv. -> main hepatic vein -> caudal vena cava -> heart
Which type of PSS usually occurs in younger animals?
Congenital PSS
- shunt occurs as a single intrahepatic or extrahepatic vessel (portal system directly into systemic circulation, bypassing the liver)
- majority of PSS cases
Which type of PSS usually occurs in older animals?
Acquired PSS
- shunt occurs 2º to chronic portal hypertension
- this type of PSS is a way of the body to adapt to the hypertension
5 types of hepatic vascular anomalies
1. EHPSS (congenital)
2. IHPSS (congenital)
3. Microvascular dysplasia (congenital)
4. Portal vein hypoplasia (congenital; causes multiple acquired shunts)
5. Multuple acquired shunts (acquired)
Pathophysiology of EHPSS
- Single vessel connecting portal venous system to caudal vena cava OUTSIDE of liver parenchyma
- Accounts for 66-75% of congenital dog/cat shunts
- Two main types: portocaval and portozygous
- small and toy breeds++
Pathophysiology of IHPSS
- Single vessel connecting portal venous system to caudal vena cava INSIDE of liver parenchyma
- Accounts for 20% of congenital dog/cat shunts
- Two main types: portocaval and portozygous
- large & giant breeds++
Pathophysiology of Microvascular dysplasia (MVD)
- Primary hypoplasia of portal vein without portal hypertension
- Microscopic malformation of hepatic vasculature
only diagnosed on a micoscope slide
Pathophysiology of Portal Vein Hypoplasia
the smaller (hypoplastic) portal vein causes increased resistance (b/c narrower vessel for blood to flow through) -> leads to portal hypertension & multiple acquired shunts
EHPSS and MVD are more common in what size dogs?
Small breeds (yorkie; pugs, maltese, mini schnauzer)
IHPSS are more common in what size dogs
Large breeds (irish wolfhounds, retrievers, aussie shepherd and cattle dog)
All hepatic vascular anomalies appear clinically the same. What are the most common signs?
- neurologic (hepatic encephalopathy+++)
- gastrointestinal
- urinary
- failure to thrive
Hepatic Encephalopathy signs
Diffuse forebrain disease
- compulsive circling or pacing; head-pressing
- seizures
- depressed level of consiousness
- ataxia
- blindness (cats)
Pathophysiology of hepatic encephalopathy
- occurs when 70% of liver function is lost
- Ammonia accumulation (GI tract is loaded with NH3 from the gut flora)
- endogenous benzodiazepines accumulation
- the accumulatd compounds impede neuronal and astrocyte function
(cell swelling & cerebral edema, inhibition of pumps/ion channels, elevated intracellular Ca2, depression of electrical activity, altered permeability of BBB)
Why do some dogs with hepatic vascular anomalies develop urethral stones?
Accumulation of ammonia in bloodstream -> accumulation of urate in urine -> excess production of ammonium biruate stones
normally converted to urea in liver
very dilute urine
Main findings on CBC/Chem of hepatic vascular anomaly patients
- microcytosis (hypoferremia)
- leukocytosis & neutrophilia (inadequate hepatic endotoxin clearance or chronic inflamm. state)
UA findings of hepatic vascular anomaly patients
Test of choice for evaluating liver function in dogs with PSS
Bile Acids Test
How to differentiate between HVA and liver failure patients on bloodwork?
Common findings on U/S of HVA?
- decreased # of portal & hepatic vv.
- small liver
- anomalous vessel
- reduced portal vein:aorta size
Gold standard for evaluating portal system and why?
CT
- can differentiate b/w intra- and extra-hepatic shunts/other anomalies
- provides complete evaluation of hepatic vasculature
How are HVAs treated?
ALL: medical management - recommended before ANY anesthesia is performed for dx or tx
- decrease NH3 (ammonia) absorption
- nutritional support
- hepatoprotective therapy
- hepatoprotective therapy
- GI ulceratino prevention (intrahepatic)
- tx/prevent hepatic encephalopathy
How to decrease NH3 absorption
- ABX
- Lactulose
HVAs: Nutritional management - diet
Moderately restrict protein
- 18-22% for dogs
- 30-35% for cats
source of high biologial protein
How are GI ulcers prevented in IHPSS patients?
PPIs (omeprazole) - LONG term//for life!!
When is surgery for PSS indicated?
- NEVER as an emergency!
- Only ever if medical management does not resolve signs after at least 2 weeks
Surgical techniques for PSS
1. Partial or complete acute occlusion (not well-tolerated/poorer prognosis - most common post-oop complications like hemorrhage)
2. Gradual Occlusion (most common)
3. Endovascular embolization (for IHPSS)
endovascular embolization: block shunt into vena cava via catheter thru jugular vein
Top 3 risk of PSS surgery?
- Portal hypertension (less common with gradular occlusion)
- Seizures (poor prognosis if they occur)
- Recurrence of Clinical Signs (most common chronic complication)
other: hypoglycemia
IHPSS: GI bleeding
Cats: (temporary) blindness
Long-term prognosis of surgical intervention in dogs versus cats
Good-to-excellent outcome in both dogs and cats (EHPSS & IHPSS for dogs, EHPSS for cats)
