Portosystemic Shunts Flashcards
What are the types of congenital PSS?
Macrovascular
- intrahepatic
- extrahepatic
Microvascular
- intrahepatic
Single shunts arise from?
Trauma or iatrogenic
Multiple shunts arise from??
Diseases that cause portal hypertension
Extrahepatic PSS are associated with what signalment ?
Small dog and cat
- YORKIES, Shih Tzu, Maltese, poodle, schauzers, dashunds, pug
What anatomy is altered in an extrahepatic portosystemic shunt?
Veins that should join the portal vein enter the caudal vena cava or azygous vein instead
Usually the left gastric vein and splenic (gastrosplenic) vein — most commonly involved
Less commonly: portocaval, gastroduodenal, mesenteric (jejunal and colic veins)
Normally, the last vessel that should enter the caudal vena cava is the ____________, any vessels entering crainal to this are abnormal shunts
Phrenicoabdominal vein (drains the adrenals)
Signalment associated with intrahepatic PSS?
Large breed
- labs
- goldens
- Australian shepherd
- Old English sheepdog (OES)
What is the abnormal anatomy occurring in an intrahepatic shunt?
Patent ductus venosus
Intrahepatic branches of portal vein enter vena cava or hepatic vein bypassing the hepatic parenchyma
What affects the major pre-haptic vessels and causes ascities more commonly than other types of congenital shunts?
Portal vein atresia
Also results in hypoproteinemia (lack of blood flow to liver)
What happens when you occlude the shunt when there is portal vein atresia?
Portal hypertension —> blood cannot flow into liver this way so blood backs up int the gastric system
How do you treat portal vein atresia??
Medically
You cannot close the shunt !!
What is the consequence of portal vein hypoplasia?
Hepatic microvascular dysplasia
—microshunting within the liver, may occur as a single entity or in conjunction with macrovascular shunts
What diagnostics can you do for portal vein hypoplasia?
Bile acids — only mildly elevated
Protein C activity >70% = microvascular shunt
—> plasma anticoagulant synthesized in liver, reflect hepatic synthetic activity and portal bloodflow
Nuclear scintigraphy
What is the treatment for portal vein hypoplasia?
Stable form— none OR medical management (diet often enough)
Progressive form - diet and medical management
Multiple extrahepatic PSS are secondary to ??
Diseases causing portal hypertension Microvascular shunt ligation Cirrhosis Non-cirrhosis portal hypertension (isopathic/ hepatic veno-occlusive disease) Hepatic A-V malformation (fistula)
How do multiple extrahepatic shunts develop from portal hypertension?
Vestigial embryonic communications “open up”
What are the general signs of microvascular shunts?
Poor growth rate, weight loss, anesthetic or tranquilizer intolerance
Lethargy, depression, weakness, behavioral changes, pacing, aggression, ataxia, stupor, head pressing, coma, seizures, blindness
Anorexia, vomiting, diarrhea, ptyalism, pica, ascities
Pu/PD, cystitis, urolithiasis, urethral obstruction
Ascities
What PE finding in cats can indicate macrovascular shunts?
Copper coloured irises
Hypersalivation
Aggressive behaviour
What do you see on CBC and biochem associated with macrovascular shunts?
Anemia, microcytosis, hhypochromasia, poikilocytosis, target cells, neutrophilia
Decreased BUN, albumin, and cholesterol
Hypoproteinemia
increased ALT and ALP
What might be present on UA that could indicate macrovascular shunts?
Low specific gravity
Ammonium biurate crystals
Uterine sed suggestive of cystitis —> hematuria, pyuria, and proteinuria
What liver fxn tests would you want to do and what would you see with a macrovascular shut?
Elevated serum bile acids — pre and post prandial
Hyperammonemia — fasting or after ammonia tolerance test
Protein C activity <70%
What is a non invasive method of diagnosis of PSS and can distinguish it from microvascular dysplasia ?
Nuclear scintigraphy
Technetium 99
—> transcolonic (higher dose needed)
—> trans-spenic (smaller dose but can often identify shunt type)
What is the most accurate non-invasive diagnostic method of PSS?
CT angiography
What is the most commonly injected vein for portography?
Mesenteric vein
How are PSS managed medically?
Diet (u/d, k/d, i/d)
Lactulose
Antimicrobial
Seizure control/ prevention
Control intestinal parasites
An albumin level of _________ makes PSS ligation much more riskier
<1.5mg/dl
What is the goal of surgery for PSS?
Divert blood flow back through portal system without creating portal hypertension (can be life threatening or can cause acquired shunts to open)
Improve liver fxn
What are the surgical management options for portosystemic shunts?
Compete ligation
Partial attenuation with suture +/- reoperation
Gradual occlusion
- ameroid constrictor
- cellophane band
- thrombogenic coils
- hydraulic occluders
How dos partial attenuation of the PSS function?
Vessel is partly occluded
Vessel may occlude spontaneously due to inflammation or altered blood flow mechanics
If it doesnt flow - reportage
How are portal pressures measured? What is the maximum acceptable change with PSS?
Catheterize and measure mesenteric vessels
Maximum change 9-10cmH2O
How does an ameroid constrictor work?
Gradual occlude
Casin ring - inflammatory thing that sweeps in contact with vessel
Complications to to closure of PSS?
Acute occlusion
- rapid closure
- kinking
Chronic
- incomplete occlusion
- acquired shunts
- implant migration
How does cellophane banding function in ligation of PSS?
Occlusion by inflammatory reaction
Typically completely occludes within 812days
What are the advantage and disadvantages to hydraulic occluders?
Advantages: single surgery w/o portal pressures, gradual and total vascular occlusion, reversible
Disadvantages: implant leakage or diffusion
How are intrahepatic shunts occluded?
Intracaval
Transportal
Thrombogenic coils
What are the acute postoperative complications with PSS ligation?
Portal hypertension Portal vein thrombosis Hypoglycemia Seizure Hemorrhage Electrolyte disturbances (hyponatremia)
