Study sets, textbooks, questions
Upgrade to remove ads
Hepatobiliary system- Bile acids and Ammonia
Exam 2 Clin Chem
Terms in this set (30)
Where are bile acids synthesized?
In hepatocytes by conjugating cholesterol with amino acids
Where are bile acids stored and when are they released?
Stored in gall bladder (in animals with gall bladders) and released at meals under influence of cholecystokinin
What happens to bile acids after being released?
In duodenum, they react with fats to form emulsion/micelles that are absorbed at the ileum
From portal vein, most bile salts undergo hepatic uptake and re-utilization
Serum levels of bile salts are affected by what?
a. GI tract (food, GI motility, GI absorption)
b. Liver (injury, cholestasis, functional mass)
C. Vascular system
What are the mechanisms that cholestasis can affect serum bile salt levels?
Obstruction- decreased canalicular BA transport- BA pumped into sinusoids vs canaliculi
TNFalpha decreases BA transport (canalicular)- possible functional cholestasis
What are the two types of sampling that can be used for bile salts testing?
Fasting + Post-prandial
When should you test for bile salts after fasting an animal?
After a 12 hour fast
Why is fasting + post-prandial testing for bile salts better than just testing after fasting?
Greater sensitivity since some animals with have ~normal resting values
Remember, a standardized meal is used
What needs to be avoided when testing for bile salts?
Lipemia and hemolysis
When should post-prandial bile salts test be taken?
2 hours after the standardized meal
~Remember: peak increase varies (1-10 hours) and may explain some odd results
~Unexpected gall bladder contraction may cause Pre- to be greater than Post-
How is RIA bile salt test different from spectrophotometry?
RIA measures specific bile salts
Spectrophotometry: measures total bile salts
What is the purpose of running bile salts test?
Confirm suspicion of decreased functional mass of the liver
How sensitive is the bile salts test for hepatobilitary disease?
VERY SENSITIVE indicator of hepatobiliary disease
How specific is the bile salts test for decreased functional mass?
NOT!!! specific for decreased functional mass
NOT very specific for the TYPES of liver disease
Why is the bile salts test not very specific for decreased functional mass?
Increase with injury, cholestasis, OR decreased functional mass
If tests for injury or cholestasis (ALT, ALP, GGT, Bc) are elevated, bile salts are often elevated even if functional mass is okay
What are some questions to ask before testing an animal for bile salts?
Is there evidence for significant cholestasis?
Is there evidence for significant hepocellular injury?
Is there significant GI disease?
Do not test these individuals since results will not be specific
What does it mean when post-Bile acids are < fasted values?
Test is NOT diagnostic value
Don't interpret, just repeat
~May reflect spontaneous gall bladder contraction
~May reflect poor CCK response
What is a negative interferent in the Bile acids test?
What are some follow up tests after bile acids?
Aspiration cytology and/or biopsy- parenchymal disease, infiltrative disease
Imaging- vascular anomalies, liver size, shape, consistency
Ammonia is a by product of what? Where does it come from?
By-product of protein catabolism
Comes from GI digestion
How is ammonia normally removed?
Removed by liver and converted to urea
What is the goal of performing an ammonia tolerance test (ATT)?
Confirm the presence of decreased functional mass (~ to bile acids)
What two types of conditions present as decreased functional mass?
Decreased liver parenchyma
How must blood be drawn for an ammonia test and what must be done after collection?
Must be drawn into ammonia-free heparin
Must be placed on ice immediately (chill collection tube prior to venipuncture)
Plasma must be separated from RBC within 20 minutes
How soon must a sample be run for ammonia test after collection?
Within 30 minutes (60 min max)
~Samples can be quick frozen and run within 2 days
What are contraindications to performing an ATT?
High resting ammonia levels
~Resting levels should be measured before risking an ammonia challenge test
Which has greater sensitivity: resting ammonia levels or ATT?
ATT (similar to postprandial bile salts)
Why might animals have high resting levels of ammonia?
1. Tho uncommon- animals w/urease producing bacterial urinary tract infections may have high resting levels of ammonia 2ndary to urea breakdown
2. Urea toxicity in cattle can cause hyperammonemia unrelated to liver dysfunction
What are the results Purdue typically sees with their ATT results?
Normal animals = A post-ATT value that is similar or less than the resting value
~+/- a mild increase (<25% of resting ammonia level) may be seen in some healthy animals
What is the typical results for ATT according to literature?
2-2.5 fold increases in healthy animals following an ATT
Sets found in the same folder
Clinical Chem- Lecture 1
Clin Chem- Lecture 2
Clin Chem- Lecture 3
Clin Chem- Lecture 4,5,6: Acid-base profiling
Sets with similar terms
Hepatobiliary: Bilirubin, Cholestasis and Function…
CBC, Chemistry and Urinalysis Interpretations
GI studies part 2 (Exam 3)
Laboratory Testing Overview
Other sets by this creator
Community Practice Block
Adv SAM Lecture 26- ITP
Adv SAM lecture 25- IMHA
Lecture 7- Guest speaker