Liver 1

Question 1

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

Answer 1

None; they are incidental and insignificant.

Question 2

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

Answer 2

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

Question 3

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

Answer 3

None; they are incidental and insignificant.

Question 4

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

Answer 4

Horses

Question 5

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

Answer 5

No-one knows.

Question 6

What is tension lipidosis?

Answer 6

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

Question 7

In which domestic species is tension lipidosis most commonly seen?

Answer 7

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

Question 8

What is the pathogenesis of tension lipidosis in cattle?

Answer 8

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

Question 9

What is the significance of tension lipidosis in cattle?

Answer 9

None; it’s incidental and insignificant.

Question 10

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

Answer 10

Camelids (llamas etc.)

Question 11

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

Answer 11

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 12

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

Answer 12

Cats and cattle

Question 13

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 13

Hepatic telangiectasia

Question 14

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

Answer 14

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

Question 15

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

Answer 15

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

Question 16

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

Answer 16

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

Question 17

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

Answer 17

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

Question 18

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

Answer 18

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 19

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

Answer 19

“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 20

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

Answer 20

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 21

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

Answer 21

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 22

What is the definition of a portosystemic shunt?

Answer 22

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

Question 23

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

Answer 23

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 24

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

Answer 24

Large breeds

Question 25

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

Answer 25

Small breeds

Question 26

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

Answer 26

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

Question 27

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

Answer 27

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

Question 28

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

Answer 28

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 29

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

Answer 29

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

Question 30

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 30

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 31

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

Answer 31

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

Question 32

What is the underlying pathogenesis of hepatic lipidosis?

Answer 32

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

Question 33

What is the characteristic histologic lesion of hepatic lipidosis?

Answer 33

Clear cytoplasmic vacuoles within hepatocytes.

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

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

Answer 35

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 36

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

Answer 36

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

Question 37

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

Answer 37

Ponies, mini horses & donkeys

Question 38

In what form is glucose stored in the liver?

Answer 38

As glycogen

Question 39

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

Answer 39

Glycogen (NOT steroids!)

Question 40

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

Answer 40

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

Question 41

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

Answer 41

Glycogen. “Steroid hepatopathy”

Question 42

What is the characteristic histologic lesion of hepatic lipidosis?

Answer 42

Clear cytoplasmic vacuoles within hepatocytes.

Question 43

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 43

Hepatic amyloid accumulation (amyloidosis)

Question 44

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

Answer 44

The spaces of Disse