Hepatobiliary System, Pt. 3

Question 1

What 6 insults commonly cause hepatocyte death?

Answer 1

1. hypoxia
2. toxins (centrilobular zone)
3. microorganisms (miliary)
4. immunological events and inflammation
5. severe metabolic disturbances
6. trauma

Question 2

What are the main patterns of necrosis an their cause?

Answer 2

1. massive (panlobular) - toxic and nutritional
2. zonal (zone 3) - toxic or hypoxia
3. multifocal random (miliary) - infectious agents, like viruses, bacteria, and protozoa

Question 3

What is a common cause of massive (panlobular) necrosis of pig liver?

Answer 3

hepatosis dietetica from a deficiency in vitamin E and/or selenium

• bright/dark red marbled necrosis affecting all lobes
• ACUTE massive mecrosis

Question 4

What is the most common form of zonal necrosis of the liver? What is it caused by? How does it look grossly?

Answer 4

centrilobular area (zone 3)

hypoxia or toxins

linear trabecular pattern of pallor necrosis affecting one zone

Question 5

What is the most common cause of multifocal random necrosis of the liver? How does it look grossly?

Answer 5

infectious agents, including viruses, bacteria, and certain protozoa

multifocal, small, miliary, pallor spots of necrosis randomly distributed throughout the liver

(equine herpesvirus infection, foal)

Question 6

What is the most common sequelae to massive chronic hepatic injury? What does it look like grossly?

Answer 6

cirrhosis, end-stage liver

multifocal nodules of regeneration after parenchymal death with fibrosis between nodules —> liver will not completely regenerate and will be smaller

Question 7

How much can the liver regenerate after damage/surgical removal?

Answer 7

70% of normal liver can be regenerated without clinical insufficiency

Question 8

What are the 3 steps to hepatic regeneration?

Answer 8

1. hepatocellular loss is replaced by proliferation of bipotential progenitor cells with the ability to mature into hepatocytes or biliary epithelium, resulting in ductular reactions and biliary hyperplasia
2. endothelial buds establish sinusoidal channels
3. hepatic stellate (Ito) cells replicate and synthesize extracellular matric rich in collagen, leading to fibrosis

Question 9

Hepatic injury and development of fibrosis:

Answer 9

damage to reticulin framework = no regeneration

Question 10

What 4 things happen during cirrhosis (end-stage liver)?

Answer 10

1. loss of hepatic parenchyma
2. nodular regeneration
3. bridging fibrosis
4. biliary hyperplasia

Question 11

What is the consequence of cirrhosis in dogs? How does this happen?

Answer 11

acquired portosystemic shunts

• hepatic fibrosis causes portal hypertension
• blood vessels unable to make it to the liver redirect to the caudal vena cava, bypassing liver sinusoids
• decrease in liver function due to decreased nutrition causes ascites

Question 12

How can nodular regeneration and nodular hyperplasia be differentiated?

Answer 12

REGENERATION = response to a loss of hepatocytes and contains fibrosis

HYPERPLASIA = common incidental finding in older dogs lacking fibrosis

Question 13

What are 6 causes of cirrhosis?

Answer 13

1. chronic toxicity
2. chronic cholangitis and/or obstruction
3. chronic congestion (right-sided heart failure)
4. inherited disorders of metal metabolism
5. chronic hepatitis
6. idiopathic

Question 14

Cirrhosis, histology:

Answer 14

n = regenerative nodules surrounded by fibrosis + loss of hepatic structure

Question 15

What is happening in the histology of this cirrhotic liver?

Answer 15

• ductular reaction of disassociated hepatocytes
• blue cells = hyperplastic biliary epithelium (usually only seen in portal triad bile duct)

+ cytokeratin 7 stain, an epithelial marker for biliary epithelium

Question 16

What are the 2 most common causes of circulatory disturbances of the liver? What are 3 other causes?

Answer 16

1. congestion
2. portosystemic shunts/vascular anomalies

• portal vein hypoplasia
• portal thrombi
• infarction

Question 17

Acute passive liver congestion:

Answer 17

• due to right-sided heart failure causing fluid back up into the liver
• dark red

Question 18

What is the most common gross presentation of chronic passive congestion of the liver?

Answer 18

nutmeg liver - central vein surrounded by a reticular pattern of pale necrosis and congestion

Question 19

What is a common cause of passive congestion in cattle? What is the pathogenesis?

Answer 19

high-altitude disease, brisket disease

• high altitude causes hypoxia and pulmonary arterial vasoconstriction
• this causes right-sided heart failure and hepatic congestion (nutmeg liver!)
• this further causes increased intravascular hydrostatic pressure, leading to ascites and peripheral edema in the brisket area

Question 20

What does the development of a portosystemic shunt cause? What are the 2 types of congenital portosystemic shunts?

Answer 20

portal blood bypasses the liver and its sinusoids

1. INTRAHEPATIC: large breed dogs; patent ductus venosus
2. EXTRAHEPATIC: cats and small breed dogs; portocaval, portoazygos

Question 21

What is a common sign of extrahepatic congenital portosystemic shunt?

Answer 21

hepatic encephalopathy due to an accumulation of ammonium —> ammonium biurate crystals in urine

(portal vein takes GI nutrients/toxins to liver, if it bypasses it, the contents of the blood directly reach systemic circulation)

Question 22

How do congenital and acquired portosystemic shunts compare?

Answer 22

CONGENITAL
- usually affects a single large caliber vessel
- NO portal hypertension or ascites (just bypassing liver, no resistance)
- early onset in young animals

ACQUIRED
- involves multiple small vessels
- associated with portal hypertension and ascites

Question 23

Congenital portosystemic shunts:

Answer 23

portal vein connects to vena cava and bypasses liver sinusoids

Question 24

How does congenital portosystemic shunts appear grossly?

Answer 24

small liver and abnormal singular vascular anastomosis

v = single anomalous vessel connecting portal circulation with systemic circulation

Question 25

What do ammonium biurate crystals look grossly?

Answer 25

thorny apple crystals in urine

• result of portosystemic shunts
• protein from diet is broken down into ammonium, but cannot react the liver to be metabolized into urea
• ammonia bypasses the liver and reaches systemic circulation (crystals and CNS signs)

Question 26

What causes acquired portosystemic shunts? What does this result in?

Answer 26

portal hypertension - external compression of vessels by tumors or abscesses, severe hepatic diseases, cirrhosis, etc.

increased hydrostatic pressure causes ascites

Question 27

How do acquired portosystemic shunts appear grossly?

Answer 27

multiple, small, tortuous anastomosing vessels, usually extrahepatic (unable to reach liver in the first place) to find its way to systemic circulation

Question 28

What are the main 2 causes of hepatic rupture?

Answer 28

1. blunt or sharp force trauma (HBC, high drops, gunshot injury)
2. predisposing hepatic disease, like hepatitis, neoplasia, fatty liver, or amyloidosis increases the fragility of the liver

Question 29

What are common causes of hepatic lobar torsion?

Answer 29

• trauma
• idiopathic

infarct of lobe leads to necrosis

Question 30

Hepatic rupture with hemorrhage:

Answer 30

fissures on lobe

Question 31

Amyloidosis with hepatic rupture and hemorrhage:

Answer 31