Lecture 4: Liver 1

Question 1

Portal hypertension can be prehepatic, intrahepatic or post-hepatic. Of these, one is more common than the other two. Which one?

Answer 1

Intrahepatic causes are most common (the other two are rare).

Question 2

What are some of the clinical signs and gross lesions seen in a puppy
with a congenital portosystemic shunt?

Answer 2

1. Stunting, relative to littermates; 2. Hepatic encephalopathy (manifesting as mental dullness); 3. Small liver size.

Question 3

Which types of equids are prone to development of hepatic lipidosis?

Answer 3

Ponies, mini horses & donkeys

Question 4

What is the characteristic histologic lesion of hepatic lipidosis?

Answer 4

Clear cytoplasmic vacuoles within hepatocytes.

Question 5

What is the cause of the fibrous tags or plaques found on the diaphragmatic surface of the liver of horses?

Answer 5

unknown

Question 6

What is the significance of tension lipidosis in cattle?

Answer 6

None; it’s incidental and insignificant.

Question 7

Where, precisely, in the liver is amyloid deposited in cases of amyloidosis?

Answer 7

The spaces of Disse

Question 8

What is the underlying cause of excessive glycogen accumulation in the liver?

Answer 8

Excessive glucocorticoids [either exogenous (iatrogenic) or endogenous (hyperadrenocorticism)]

Question 9

What is hepatic telangiectasia? What does it look like grossly?

Answer 9

Randomly scattered areas of dilation of hepatic sinusoids by blood where hepatocytes have been lost. Grossly, it appears as dark red “dit-dots” and patches throughout hepatic parenchyma.

Question 10

What histologic changes would you expect in the liver of an anemic animal?

Answer 10

Centrilobular hepatocyte degeneration and necrosis with dilation and congestion of centrilobular sinusoids by blood. [Note that “enhanced reticular pattern” is a gross, not a histologic change and is not an acceptable answer, sorry.]

Question 11

In which phases or periods are cattle most susceptible to developing hepatic lipidosis, and why?

Answer 11

Fat cows in late gestation, immediately post partum or in peak lactation. Excessive mobilization of body fat stores to cope with demand overwhelms liver’s ability to process and export it –> accumulation.

Question 12

What is the characteristic histologic lesion of hepatic lipidosis?

Answer 12

Clear cytoplasmic vacuoles within hepatocytes.

Question 13

What is the underlying pathogenesis of hepatic lipidosis?

Answer 13

The rate of accumulation of triglycerides within hepatocytes exceeds the rate of their removal

Question 14

What is the most common reason for chronic passive congestion in the liver?

Answer 14

Chronic right-sided heart failure (for a variety of reasons)

Question 15

Excessive administration of glucocorticoids by veterinarians can cause what substance to accumulate in the liver? What is the term for this condition?

Answer 15

Glycogen. “Steroid hepatopathy”

Question 16

What is tension lipidosis?

Answer 16

Areas of pallor in hepatic parenchyma where the liver is suspended by ligaments.

Question 17

You are performing a necropsy on a bird euthanized for chronic foot infections and notice that the liver is swollen, pale, waxy and friable. What is the most likely cause of the liver lesion?

Answer 17

Hepatic amyloid accumulation (amyloidosis)

Question 18

What is the characteristic signalment and scenario for a cat that develops hepatic lipidosis?

Answer 18

Obese cat –> stressed (disease, change of environment etc.) –> goes off food for several days –> idiopathic accumulation of lipids in hepatocytes.

Question 19

What is the gross appearance of a liver with acute passive congestion (give 3 gross findings)?

Answer 19

1. Slight hepatomegaly; 2. Enhanced reticular pattern / centrilobular congestion; 3. Oozes blood from cut surfaces

Question 20

In what type of animal is the edge of the liver fimbriated or “frilly”?

Answer 20

Camelids (llamas etc.)

Question 20

In which domestic species are fibrous tags or plaques often found on the diaphragmatic surface of the liver?

Answer 20

Horses

Question 21

What is the most common reason for an INTRAhepatic congenital portosystemic shunt?

Answer 21

Intrahepatic congenital PSSs are generally due to failure of closure of the ductus venosus at birth. [The ductus venosus is a normal fetal vessel that conducts blood from the umbilical vein to the caudal vena cava.]

Question 22

Describe the gross appearance of a liver affected by hepatic lipidosis.

Answer 22

Enlarged, friable, pale, greasy, may float in formalin

Question 23

Explain the difference between the terms “nutmeg liver,” “enhanced lobular pattern” and “enhanced reticular pattern.”

Answer 23

“Enhanced lobular pattern” and “enhanced reticular pattern” mean the same thing and are interchangeable terms. Both refer to any repeating lesion within all hepatic lobules, including (for example) periportal inflammation or cancer, centrilobular necrosis, and midzonal glycogen accumulation (i.e., anything that causes a repeating dark-light pattern at the level of every hepatic lobule). “Nutmeg liver” is a form of enhanced lobular pattern reserved for the chronic passive congestion associated with chronic right sided heart failure.

Question 24

In which breeds of dogs (large or small) are INTRAhepatic congenital portosystemic shunts more common?

Answer 24

Large breeds

Question 25

In what form is glucose stored in the liver?

Answer 25

As glycogen

Question 26

What is the definition of a portosystemic shunt?

Answer 26

An abnormal vascular channel that allows portal blood to bypass the liver and enter the systemic circulation.

Question 27

What accumulates in the cytoplasm of hepatocytes in so-called “steroid hepatopathy”?

Answer 27

Glycogen (NOT steroids!)

Question 28

In which two domestic species is hepatic telangiectasia most commonly seen?

Answer 28

Cats and cattle

Question 29

Portal hypertension caused by intrahepatic disease is far more common that that caused by prehepatic or posthepatic disease. What are two common, underlying mechanisms for intrahepatic portal hypertension?

Answer 29

1. Chronic liver disease with loss of architecture & fibrosis; 2. Hepatic accumulations e.g., amyloid. [Both cause increased resistance to blood flow through liver.]

Question 30

You are performing a necropsy examination on a cat and find dozens of dark red foci throughout its liver parenchyma and over the capsular surface of the liver. What are these lesions most likely to be?

Answer 30

Hepatic telangiectasia

Question 31

Describe 3 key histologic findings in a liver with chronic passive congestion

Answer 31

1. Centrilobular congestion; 2. Centrilobular hepatocyte atrophy and/or necrosis; 3. Periportal hepatocyte lipid accumulation. To summarize: the centres of lobules are dark because of accumulation of “stagnant” blood and loss or compression of hepatocyte plates, while the peripheral areas of lobules are pale because hypoxic hepatocytes have accumulated lipid. This repeating dark-light pattern is called “nutmeg liver.”

Question 32

In which domestic species is tension lipidosis most commonly seen?

Answer 32

Cattle, and less commonly in horses (i.e., large animals with heavy livers).

Question 33

What is the most common reason for acute passive congestion in the liver?

Answer 33

Acute right-sided heart failure (for a variety of reasons)

Question 34

Explain how toxic or hypoxic damage to hepatocytes can cause hepatic lipidosis.

Answer 34

Hepatocellular injury –> Reduces ability to process, transform & export lipids –> Accumulation within cytoplasm of hepatocytes.

Question 35

Anemia can cause an enhanced lobular pattern grossly and centrilobular hepatocyte degeneration and necrosis microscopically. Explain the pathogenesis of this pattern of injury.

Answer 35

Centrilobular hepatocytes receive blood last and so receive the least oxygenated blood in the liver. Therefore, hypoxia caused by anemia hits the centrilobular hepatocytes the hardest –> degeneration or death of centrilobular hepatocytes, while periportal hepatocytes may be spared.

Question 36

What is the significance of several biliary cysts in the liver parenchyma?

Answer 36

None; they are incidental and insignificant.

Question 37

What are 2 histologic lesions are seen in the liver of a puppy with a congenital portosystemic shunt?

Answer 37

1. Small or absent portal veins in portal areas; 2. “Arteriolar reduplication” in portal areas

Question 38

What is the significance of fibrous tags or plaques found on the diaphragmatic surface of the liver of horses?

Answer 38

None; they are incidental and insignificant.

Question 39

What is the pathogenesis of tension lipidosis in cattle?

Answer 39

Tension on liver by suspensory ligaments –> impedes blood flow –> localized hypoxia –> localized lipid accumulation –> areas of pallor

Question 40

What is the gross appearance of a liver with chronic passive congestion (give 3 gross findings)?

Answer 40

1. Hepatomegaly; 2. Rounded edges to liver; 3. Enhanced reticular pattern (“nutmeg liver”)

Question 41

What is the most common underlying reason for development of an acquired (not congenital) portosystemic shunt?

Answer 41

Portal hypertension. [Portal blood can’t pass through the liver and so creates an “escape valve” to give itself some way back into the systemic circulation.]

Question 42

In what key way do congenital biliary cysts differ from the cysts in the liver associated with polycystic kidney disease?

Answer 42

In number. Congenital biliary cysts are few, whereas those associated with PKD are much more numerous.

Question 43

In which breeds of dogs (large or small) are EXTRAhepatic congenital portosystemic shunts more common?

Answer 43

Small breeds