IIA4 - Organ Function Testing Flashcards
(42 cards)
By what process does bilirubin build up with liver disease?
The liver converts unconjugated bilirubin into conjugated bilirubin which is more water soluable which is then excreted into the bile
Bilirubin can build up with liver disease that prevents conjugation or with bile stasis that prevents excretion
By what process are bile acids increased with liver disease?
Bile acids are excreted into the GI tract during digestion, then are reabsorbed though enterohepatic circulation and by cellular transporters on hepatocytes
If the enterohepatic circulation is bypassed by a shunt, or if hepatocytes are damage such that they cannot reuptake the bile acids - the bile acids build up in the blood
Why do horses (unlike dogs) only need a single time point for bile acid testing?
Horses do not have a gallbladder
What is different about bile acid testing in cattle compared to other animals?
Cattle have a wider range for bile acid levels in normal animals so bile acids are a less sensitive test for hepatic disease in cattle
In what scenarios may bile acid levels be falsely decreased?
If there is concurrent small bowel disease
Bile acids are not taken into the enterohepatic circulation (into the blood) and are instead lost in the feces
When is an ammonia tolerance test contraindicated?
If hyperammonemia is already present, performing an ammonia tolerance test is unnecessary and potentially risks severe neurologic deterioration
How long after administering ammonium chloride should ammonia levels be collected during an ammonia tolerance test?
30 minutes
What is the expected result of an ammonia tolerance test in animals with hepatic dysfunction?
An ammonia value that is 3-10x the baseline value
What % of hepatic dysfunction must occur before hyperammonemia will be observed?
70%
What is hepatic photosensitivity in cattle and what is its cause?
Inflammation and necrosis of the unhaired or unpigmented regions of skin
Breakdown of chlorophil produces phylloerythrin which is taken up by and excreted by the liver. Liver disease allows phylloerythrin to build up in the blood which accumulates in the skin and sensitizes the skin to sunlight
What % of hepatic dysfunction must occur before changes in glucose homeostasis (hypoglycemia) may be observed?
70%
By what three mechanisms does hypoglycemia develop in animals with liver dysfunction?
1) Decreased hepatic update of glucose
2) Decreased glycogen stores in the liver
3) Decreased insulin clearance
What are changes in albumin levels not typically seen with acute liver dysfunction?
Albumin has a long half life so it can take time to see the effect of liver dysfunction on albumin levels
How is hemostasis affected by hepatic dysfunction?
The liver produces fibrinogen and K-dependant clotting factors (II, VII, IX, and X)
With liver dysfunction, these clotting factors decrease
What chemistry findings may be abnormal with liver dysfunction?
Decreased:
* Alb
* Chol
* BUN
* Glu
Increased:
* tBili
* Ammonia
* Bile acids
What affect does PTH and PTHrp have on each of the following parameters?
1) Calcium
2) Phosphorous
3) Vitamin D
1) Calcium increases
2) Phosphorous decreases
3) Vitamin D increases
What test is best for evaluating calcium levels for hypo- or hypercalcemia?
Ionized calcium
Hypomagnesemia may be associated with what clinical condition in ruminants?
Grass tetany
What conditions can lead to grass tetany in cattle?
Typically occurs in cattle fed on lush pastures that are high in potassium and low in magnesium which impact magnesium absorption and leads to clinical hypomagnesemia
What are the clinical signs of hypomegnesemia (grass tetany) in cattle in the following severities?
1) Mild disease
2) Severe disease
1) Mild cases typically show reduced milk production, restlessness, and hyper-alertness
2) Severe cases often become recumbent with muscle twitching, spasming, paddling, and ultimately death
What is the best test for identifying hypomagnesemia in cattle?
Urine magnesium testing
In a dog, a decreased total T4 test result may be indicative of what?
Hypothyroidism is possible but can also occur with non-thyroidal illness.
Further thyroid testing (free T4, and TSH) is indicated
In a dog, a normal total T4 test result would be indicative of what?
Hypothyroidism can be ruled out
In a dog, an increased total T4 test result would be indicative of what?
10% of hypothyroid dogs will have an elevated total T4 due to anti-T4 antibodies but can also occur extremely rarely in conditions like thyroid carcinoma
T4 auto-antibody testing should be performed
