Test for hepatic, intestinal and pancreatic function and integrity

Question 1

What can you test with the liver?

Answer 1

• 1. Hepatocellular injury =
• damage to hepatocytes leading to leakage of enzymes
• 2. Cholestasis =
• reduced/blocked bile excretion
• release of enzymes induced by retained bile
• 3. Hepatocellular function =
• decreased production or catabolism of substances
• 4. Hepatic portal circulation
• decreased extraction of substances absorbed from the GI

Question 2

What are liver enzymes?

Answer 2

• ALT = largely liver specific (+muscles also) - small animals
• AST + LDH = liver + muscle
• SDH + GLDH = liver specific in all species - used in large animals (SDH unstable)

(ALP + GGT indicative of liver damage in horses)

Question 3

What can increase in AST + LDH indicate?

Answer 3

• Can be artefact due to Haemolysis - check serum / plasma quality

Question 4

What can cause mild increase in AST, LDH +/- ALT?

Answer 4

• Myocyte damage or liver damage - check CK

Question 4

What are cholestatic enzymes?

Answer 4

• ALP
• GGT

Question 5

What are the half life of liver enzymes in dogs/cats?

Answer 5

• Days in dogs
• Hours in cats = small increases may be significant

Question 6

What are components of bile?

Answer 6

• Bilirubin
• Bile acids
• Cholesterol

Question 7

What are different types of hyperbilirubinaemia?

Answer 7

• Prehepatic = secondary to haemolysis (anaemia)
• Hepatic = due to decreased bilirubin uptake, conjugation and excretion
• Post-hepatic = secondary to obstruction of the extrahepatic bile duct

Question 8

What can you measure with bilirubin?

Answer 8

• Total bilirubin
• Conjugated bilirubin

Question 9

What are clinical signs of hyperbilirubinaemia?

Answer 9

• Jaundice - persists for long after liver function returned to normal (due to delta-bilirubin)

Question 10

What is the function of the liver?

Answer 10

• Detoxification of Body Wastes, Xenobiotics and Drugs
• Synthesis of Plasma Proteins
• Storage of Glycogen, Iron, Copper and Vitamins
• Breakdown of RBC (degradation of haem)
• Synthesis of Cholesterol and Bile Acids
• Production of Clotting Factors
• Removal of Bacteria
• Carbohydrate, Lipid and Amino Acid Metabolism

Question 11

How can you test hepatocellular function?

Answer 11

1. Decreased uptake and excretion of bilirubin and bile acids
2. Decreased conversion of ammonia to urea
3. Decreased synthesis of metabolites
4. Decreased synthesis of coagulation proteins
5. Decreased immunologic function

Question 12

What cause alterations to hepatic blood flow?

Answer 12

• 1. Decreased uptake and excretion of bile acids
• 2. Decreased conversion of ammonia to urea
• 3. Decreased immunologic function

Question 13

What is the significance of raised ammonia?
When would you get raised ammonia levels?

Answer 13

• Hepatic encephalopathy
• Elevated in -
  – Congenital and acquired portosystemic shunts
  and liver failure

Question 14

What can cause increased bile acids?

Answer 14

• Reduced uptake/excretion by hepatocytes
  – Reduced hepatocellular mass
  – Impaired hepatocyte function
• Disruption of enterohepatic circulation
  – Portosystemic shunts
  – Cholestasis/bile obstruction

Question 15

What are different SBA tests? (serum bile acids)

Answer 15

• Fasting SBA (>25-30mmol/L = abnormal)
• Post prandial SBA (>25-30mmol/L = abnormal)

Question 16

What extra hepatic diseases cause elevation in liver enzymes?

Answer 16

• Hypoxia
• GI + pancreatic disease
• Endocrine diseases
• Sepsis

Question 17

What can you see on haematology of liver disease?

Answer 17

• Microcytosis = (portosystemic shunts or severe liver insufficiency, likely due to altered iron transport or metabolism)
• Ovalocytes = (elliptocytes) are frequently seen in cats with hepatic lipidosis
• Acanthocytes
  – lipid disorders
  – disruption of normal vasculature (eg, hepatic hemangiosarcoma)

Question 18

What is seen on urinalysis of liver disease?

Answer 18

• Isosthenuria or inappropriately low USG
• Bilirubinuria (more than 2+ in dogs, any in cats)
• Ammonium biurate crystals or uroliths (40- 70% of patients with portosystemic shunts)

Question 19

Whats the difference between liver damage and liver function?

Answer 19

• Liver damage = Increased ALT, AST and GLDH
• Decreased Liver function = Increased bilirubin and ammonia, decreased urea and decreased albumin

Question 20

What is the function of the endocrine pancreas?

Answer 20

• Secrete insulin + glucagon
• Regulate glucose
  (2% of pancreas)

Question 21

What does the exocrine pancreas do?

Answer 21

• Secrete enzymes involved in initial digestion of food
  (98% of pancreas)

Question 22

What are the digestive enzymes secreted by the pancreas?

Answer 22

• Proteases = trypsin, chymotrypsin, elastase
• Lipases
• Amylase
  + bicarbonate

Question 23

What are tests for exocrine pancreas integrity?

Answer 23

Enzyme assay for amylase + lipase
* Amylase = catalyses hydrolysis of complex starches
(DOGs) - can increase due to decreased GFR
* Lipase = catalyses hydrolysis of triglycerides (can also increase due to decreased GFR)
* DGGR Lipase test

Question 24

What additional test to DGGR lipase would you want to do to diagnose pancreatitis?

Answer 24

• PLI
• Imaging (ultrasound)
• Fluid analysis
• Biopsy

Question 25

What are tests for exocrine pancreas function?

Answer 25

• TLI = trypsin-like immunoreactivity
• used in dogs, cats + horses
• detects exocrine pancreatic insufficiency (EPI)
• less useful for pancreatitis
• if serum TLI <2.5ug/L in dogs = EPI
• if serum TLI <8mg/L = EPI in cats