Clinical pathology

Question 1

What biochemical markers would you look for to indicate active hepatocellular damage?

Answer 1

AST (general cell damage- usually liver or muscle cells)
LD (general cell damage- all species)
ALP (hepatocyte damage- dog/cat)
ID or GD (hepatocyte damage- horse)

Question 2

What biochemical markers would you look for to indicate cholestasis?

Answer 2

ALP (in dog and cat)

GGT (dog, cat, horse, ruminants- better indicator than ALP in cats because it has a longer half life)

Question 3

What biochemical markers would you look for to indicate cholestasis and cell damage?

Answer 3

Bilirubin- total, conjugated and unconjugated

Question 4

What biochemical markers would you look for to indicate reduced functional hepatic mass?

Answer 4

Bile acids, bromsulphophthalein, blood ammonia/urea, serum proteins

Question 5

What biochemical markers would you look for to indicate pancreatic acinar damage?

Answer 5

AMS or ALP

Question 6

Greater damage to fewer cells results in less ALT while less damage to more cell results in more ALT- true or false?

Answer 6

True

Question 7

In the absence of tissue damage, what factors may result in increased ALT in dogs?

Answer 7

ALT production may be induced by corticosteroid application and some anticonvulsants

Question 8

What is meant by the term “induced enzymes”?

Answer 8

Release is triggered by changes in the liver or by application of corticosteroids

Question 9

Why might ALP or GGT appear to be elevated in neonatal puppies or kittens?

Answer 9

Ingested in colostrum

Question 10

What might a mild- marked elevation in ALP mean int eh dog when compared to a moderate to marked elevation?

Answer 10

Mild-marked: cholestasis
Moderated- marked: hyperadrenocorticism or exogenous corticosteroids
[GGT is not effected by barbiturates or anticonvulsants but can be induced by corticosteroids]

Question 11

Would you consider mildly elevated ALP in a cat to be significant?

Answer 11

Any elevation in ALP in cats is considered significant regardless of magnitude

Question 12

What methods can be used to measure bilirubin?

Answer 12

Urine bilirubin, urine urobilinogen, serum bilirubin and faecal bile pigments

Question 13

Why may a slight increase in urine bilirubin in a dog not be considered significant?

Answer 13

Only conjugated bilirubin can be excreted by the kidneys–> gives an indication of serum bilirubin
Male dogs have the capacity to break down haemoglobin and conjugate bilirubin
Dogs also have a low renal threshold to conjugated bilirubin

Question 14

What would urobilirubinuria in a cat or a horse indicate?

Answer 14

Elevated serum conjugated bilirubin

Question 15

What is the name of the test used to determine the levels of conjugated vs unconjugated bilirubin?

Answer 15

Van den Bergh’s test

Question 16

Describe the traditional classification of hyperbilrubinaemia

Answer 16

1. Haemolytic: non-cholestatic, excess production of bilirubin –> pre-hepatic
2. Hepatocellular: non-cholestatic and intrahepatic cholestasis, reduced excretion –> hepatic
3. Obstructive: post-hepatic

Question 17

Describe the preferred classification of hyperbilirubinaemia

Answer 17

1. Retention hyperbilirubinaemia: increased unconjugated hyperbilirubin in blood +/- hyperbilirubinuria. Usually due to haemolytic crises
   - -> pre-hepatic
2. Regurgitation (cholestatic) hyperbilirubinaemia: predominant form is conjugated; usually + bilirubinuria. Due to cholestasis at hepatocyte level (inflammation or neoplasia) through to gut; intrahepatic/ extrahepatic obstruction
   - -> hepatic/ post-hepatic
3. Combined hyperbilirubinaemia: develops from a combination of retention and regurgitation methods resulting in conjugated and unconjugated bilirubinaemia. Due to a variety of liver diseases

Question 18

Why is retention hyperbilirubinaemia the most common form of hyperbilirubinaemia in horses and ruminants?

Answer 18

Caused by anorexia– VFAs produced in starvation state compete for ligand binding sites

Question 19

What is the most common form of hyperbilirubinaemia in dogs and cats?

Answer 19

Combined hyperbilirubinaemia