Bile salts/ ammonia

Question 1

Enterohepatic cycle

Answer 1

Bile Salt – produced in hepatocyte
(Taurine conjugation – AA + Cholesterol)
–> gall bladder for storage

Meal stimulates

• -> CCK –> contraction of gall bladder
• -> Bile into duodenum
• -> emulsifies fats
• -> Micelles –> absorbed at ileum
• -> Portal vein –> hepatic uptake –> reutilization

**cycle is too efficient to detect ↓ bile salt production

Question 2

Is serum bile acids specific for ↓ hepatic fxn

Answer 2

NO

• GI tract
• Liver - injury, cholestasis, heptic fxn
• vascular system

Question 3

3 mechanisms for ↑ serum bile acids

Answer 3

-

Question 4

3 considerations for sample handling w/ Ammonia measurements

Answer 4

1. Ammonia-free heparin – lithium preferred
2. Place on ice immediately
3. Plasma separated w/in 20mins, run by 30mins

Question 5

2 general conditions that result in ↑ ammonia / ammonia tolerance test (unrelated to liver dysfxn)

Answer 5

1. Urea toxicity in cattle
   
   • unrelated to liver dysfxn
2. UTI (urease-producing bacteria)

Question 6

6 alterations on chem panel that signal need for bile salt/ammonia evaluation

Answer 6

-

Question 7

CBC / coagulation / UA alterations that signal need for bile salt/ammonia evaluation

Answer 7

-

Question 8

Differentiation btwn hepatic insufficiency & vascular shunting

Answer 8

• cytology
• imaging
• surgery

Question 9

How does cholestasis cause ↑ bile salt

Answer 9

• obstruction

• -> ↓ canalicular Bile acid transport
• -> BA’s pumped into sinusoids (vs canaliculi)

Question 10

Fasting + Post-prandial

Answer 10

Greater sensitivity

• standard meal (science diet A/D)
  - uniform gall bladder stimulation/ GI motility
• avoid Lipemia & Hemolysis
  - -> interfere w/ bile acids
• Post-parandial sample @ 2hr

Question 11

Assays for Bile acids

Answer 11

1. Radioimmunoassay (RIA)
   - Taurine conjugate specifically
2. Spectrophotometry
   - TOTAL bile salts

Question 12

Causes for ↑ Bile acids

Answer 12

1. evidence for significant cholestasis
2. evidence for significant hepatocellular injury
3. Significant GI dz
4. Loss functional mass

** must pick appropriate patient

Question 13

What does it mean if you Post-BA < fasted value?

Answer 13

REPEAT the sample!
- spontaneous gall bladder contraction
(smelled/saw food)
- Poor CCK response (didn’t eat the food

Question 14

When do you NOT use ammonia challenge test?

Answer 14

• seizure
• non-responsive
• listless
• debilitated patient
• high resting levels

Question 15

ATT results

Answer 15

< 25% of resting levels = healthy animals

Abnormal – ???