Liver and Pancreas Clin Path Flashcards
what 2 things are necessary to globally determine liver health?
both hepatic enzymes AND indicators of liver function!!!
what are the 2 types of hepatic enzymes?
- those that indicate hepatocellular damage
- those that indicate cholestasis
what is cholestasis?
interruption or obstruction of bile flow or excretion, with the slow flow of bile, enzymes have time to chew on hepatocytes, so cause those hepatocytes to slough off into blood, taking the enzyme with them and increasing that enzyme level in blood
describe hepatic enzymes that indicate liver damage (3) and give 3 examples
- released with hepatocyte damage or necrosis
- blood increases can be seen just hours after injury or damage
- many species differences between species so panels vary
examples are: ALT, AST, SDH
describe cholestatic enzymes (4) and give 2 examples
- membrane bound
- cholestatic enzymes are not the best name for these enzymes because other things can cause increases in these enzymes as well
- increases in levels of these enzymes in blood take days, not hours
- again, species differences so panels vary
examples are: ALP and GGT
describe ALP (what is stands for and the sources)
- stands for alkaline phosphatase
- total ALP is comprised of sources from liver (the top contributor), bone, and also corticosteroid induced in dogs
what do blood increases in ALP indicate? (3, plus a 4th for dogs only)
- cholestasis
- bone remodeling in young growing animals since panel values have reference intervals for adults
- animal hit by car or with a bone tumor could also be a reason for bone remodeling
- induction by steroidal drugs in dogs only!
what could a blood increase in GGT indicate? what does GGT stand for?
GGT = gamma glutamyl transferase
1. cholestasis
2. steroids (dogs only and is minimal so not worth investigating
3. colostrum ingestion in DOGS, SHEEP, and CATTLE (neonates, 7-10 days old); NOT cats or horses so if see elevated GGT in kittens or foals, investigate!!
do increases in liver enzymes indicated a loss of function? how is it best to measure these enzymes?
nope! remember, must evaluate both enzymes AND liver function!! and serial measurements are much more helpful to understand the full picture
what kind of substances are indicators of liver function? (2)
substances that are
1. synthesized by the liver or
2. removed from the blood by the liver
when are changes in the substances that indicate liver functions typically seen?
not until 60-70% of the functional liver mass is gone (AKA: liver is fucked)
list the substances (5) and the change in the substance observed on a liver panel if liver function is compromised
- albumin: decrease
- cholesterol: decrease
- urea nitrogen (BUN): decrease
- glucose: decrease
- bilirubin: INCREASE
what is a systemic change observed if liver function is compromised?
decreased production in coagulation factors
how does albumin reflect normal liver physiology?
all albumin is synthesized in the liver, so loss of 60-80% liver function leads to hypoalbuminemia
how does urea nitrogen indicate liver function? (BUN)
hepatocytes convert ammonium to urea, so if there is liver dysfunction there is less synthesis of urea
how does cholesterol indicate liver function? give exception with cholestasis
liver synthesizes cholesterol so liver dysfunction = lower cholesterol, but cholestasis blocks clearance of cholesterol and actually causes cholesterol to increase
how does glucose indicate liver function?
the liver is important for gluconeogenesis, so decreased liver function would lead to a decrease in glucose, BUT more than 75% of liver mass must be lost before hypoglocemia occurs as it is one of the last changes to appear since glucose is so vital to the body
how does bilirubin indicate liver function?
bilirubin is a pigment produced by the degradation of heme, which occurs in the liver, and total bilirubin is comprised of unconjugated and conjugated bilirubin
give the 3 types of hyperbilirubinemia and their causes
hyperbilirubinemia can be pre-hepatic (due to increased hemolysis)
hepatic (due to anorexia in horses and cattle, decreased functional liver mass, or intrahepatic blockages)
or post-hepatic (due to decreased secretion into biliary system or post-hepatic cholestasis/pancreatic disease)
describe how evaluation of serum bile acid and ammonia levels reflect the health of the liver and enterohepatic circulation
bile acid: the liver makes bile acids, which are then secreted into bile and transported to the duodenum, most are then reabsorbed into portal blood or excreted via feces; so normally there will be a peak in bile acids post meal that will return to healthy levels in 2+ hours, but liver dysfunction will lead to prolonged blood increases in bile acids (this test can be affected by cholestasis, spontaneous gall bladder contraction pre-sample, and concurrent intestinal disease)
ammonium: derived from dietary proteins; decreased clearance of ammonia due to liver damage, leading to hyperammonemia; not affected by cholestasis but the drawback is the sample must stay on ice and be processed super quickly so if live far from lab, will not be able to run this test
identify how amylase is used to assess exocrine pancreatic health
amylase: can come from the pancreas, or from small intestine, liver, and even salivary ducts in pigs and humans (multiple sources = less accurate picture of pancreatic health); cleared by kidneys majorly and some by the liver (clearance by other organs also affects picture of pancreatic health)
increase amylase could indicate (3):
1. pancreatic acinar cell damage due to inflammation or neoplasia
2. decreased clearance due to decreased glomerular filtration rate or liver disease
3. intestinal disease/obstruction
decreased amylase is not clinically significant
identify how lipase is used to assess exocrine pancreatic health
lipase is produced by the pancreas but also by the stomach, liver, and endothelium (hard to determine pancreatic health due to multiple sources) and cleared by the kidneys (clearance by other organs also means hard to use to assess pancreatic function)
increased lipase could indicate (3):
1. pancreatic acinar cell damage due to inflammation or neoplasia
2. decreased clearance due to decreased glomerular filtration rate
3. corticosteroids: in dogs
decrease lipase is often an artifactual finding
describe how pancreatic lipase immunoreactivity indicates exocrine pancreatic health
this is an immunoassay that determines that concentration of pancreatic lipase, not the enzymatic activity, so the pancreas is the only source being evaluated and a much more specific test that is not affected by renal function or corticosteroids in dogs!!
increased PLI is indicative of pancreatitis when correlated with clinical signs and imaging
decreased PLI is associated with reduced functional pancreatic acinar tissue mass, as a result of chronic pancreatitis or exocrine pancreatic insufficiency (there is a better test for EPI though hold please)
how is trypsin-like immunoreactivity indicative of exocrine pancreatic health?
measures trypsin and trypsinogen concentration, where the pancreas is the predominant source, so is the test of choice to diagnose exocrine pancreatic insufficiency!
however, trypsin is cleared by the kidney so renal function could affect this test
increased TLI is indicative of (3)
1. pancreatitis (inconsistent bc renal interference)
2. decreased glomerular filtration rate
3. postprandial (after a meal, animal ate recently)
decreased TLI could indicate:
1. maldigestion/malabsorption due to exocrine pancreatic insufficiency!! or intestinal disease
2. decreased release from pancreatic cells due to chronic pancreatitis or pancreatic acinar atrophy
how is the endocrine pancreatic health evaluated?
hyperglycemia can indicated transient acute pancreatitis; pancreas plays a role in glucose homeostasis
