Portosystemic Shunts

Question 1

What is a portosystemic shunt?

Answer 1

aberrant vessel from the portal, left gastric, or splenic vein drains into the vena cava or azygous vein, bypassing the liver and detoxification

Question 2

What signalment is most commonly associated with portosystemic shunts? What kind of shunt is most common?

Answer 2

small breeds less than 1 y/o –> Yorkies, Maltese, Pugs, Miniature Poodles, etc.

single, congenital, extrahepatic (large breeds most commonly have intrahepatic)

Question 3

What unique presentation is seen in cats with a portosystemic shunt?

Answer 3

cooper colored eyes

Question 4

What clinical signs are indicative of portosystemic shunts?

Answer 4

• undersized for breed compared to littermates
• polyphagia
• vomiting, diarrhea, PU/PD
• neurological deficits or inappropriate behavior especially after eating (hepatic encephalopathy)

Question 5

How is the CBC affected by portosystemic shunts?

Answer 5

initial normocytic, normochromic anemia progresses to microcytic and hypochromic

Question 6

What are 5 possible changes to blood chemistry associated with portosystemic shunts?

Answer 6

1. variable liver enzyme changes - elevated ALP
2. decreased BUN
3. decreased albumin
4. decreased glucose
5. decreased cholesterol

Question 7

What is used to test liver function in cases of portosystemic shunts?

Answer 7

bile acids

• dramatically elevated post-prandial bile acids

Question 8

How are ammonia levels affected by portosystemic shunts?

Answer 8

elevated

• this measurement is more sensitive compare to bile acids, but it must be performed immediately after a blood draw

Question 9

How is the UA affected by portosystemic shunts?

Answer 9

ammonium biurate crystal development

Question 10

What are 5 possible ways of imaging to diagnose portosystemic shunts?

Answer 10

1. microhepatica on radiographs
2. aberrant vessel or urate stones in the bladder on U/S
3. mesenteric portovenogram
4. transcolonic scintigraphy - contrast absorbed through the colon will go directly to the liver first via portal circulation, but it will bypass the liver and seen in the heart first
5. transplenic scintigraphy

Question 11

What are 4 important parts to the medical management of patients with portosystemic shunts? What is their prognosis like?

Answer 11

1. Metronidazole or Neomycin - decreases urease-producing bacteria in colon (neomycin is not absorbed through the GI tract!)
2. Lactulose - decreases colonic pH, resulting in decreased ammonia absorption
3. low-protein diet - decreased substrate for ammonia production
4. potassium bromide - seizuring, lactulose enemas

shortened lifespan –> surgery is recommended for a normal lifespan

Question 12

What is part of surgical management of portosystemic shunts? What are 3 options?

Answer 12

surgical closure of the aberrant shunting vessel

1. ameroid constrictor - gradual occlusion
2. cellophane band - gradual occlusion
3. partial or complete ligation - greater portal hypertension and complication rate

Question 13

What needs to be monitored post-op in the occlusion of portosystemic shunts?

Answer 13

• evidence of hypoglycemia
• seizures
• excruciating pain –> complete occlusion leading to portal hypertension

Question 14

What should always be done when going into surgery to occlude a portosystemic shunt? Why?

Answer 14

obtain a liver biopsy

rule in or out microvascular dysplasia - shunting at the level of the hepatocyte –> no cure at the time