Liver Fnc Tests Flashcards
the liver produces?
bile
what does bile do?
fat absorption, excretion of bilirubin, excess copper
the liver stores?
glycogen, triglycerides, iron, copper, fat-soluble vitamins
the liver detoxifies?
ammonia (endogenous), alcohol & drugs (exogenous)
the liver synthesizes?
important plasma proteins, such as ambumin, coagulation factors, and complement proteins
the liver has a central role in the metabolism of?
protein, fat, and carbohydrates
LFTs are used to?
detect liver dz, direct diagnostic workup, estimate disease severity, assess prognosis, and evaluate response to tx
which LFTs identify hepatocellular injury?
aminotransferases (ALT, AST)
which LFTs are markers of cholestasis?
alkaline phophatase (AP), g-Glutamyl transferase (GGT), and bilirubin
which tests measure the synthetic function of the liver?
prothrombin time (PT), albumin, and bilirubin (which the liver conjugates for excretion, but does not make)
where is hemoglobin metabolized?
spleen and other macrophage-containing tissues
what happens to the protein compoents of hemoglobin?
broken down into AA and recycled
___ cannot be recycled and is catabolized to bilirubin
heme
native bilirubin is also referred to as?
unconjugated bilirubin
is bilirubin polar or nonpolar? Soluble or insoluble?
polar; insoluble
how is bilirubin transported to the liver?
tightly, but non-covalently bound to albumin
what prevents bilirubin from being filtered by the kidney?
being bound to albumin
when is unconjugated bilirubin found in urine?
when there is a spillage of albumin, such as with nephrotic syndrome
unconjugated bilirubin becomes water-soluble when it is conjugated to _____
glucuronic acid
conjugated bilirubin is first excreted into the ____
bile
conjugated bili enters the GI tract at the?
ampulla of Vater
_____ in the colon metabolize conjugated bili to _____
bacteria, urobilinogen
the majority of urobilinogens go where?
eliminated in feces
of the small fraction of urobilinogen absorbed into the circulation, what two pathways can it take?
picked up by liver for re-excretion OR excreted in the urine
after intrcellular binding in the liver, what conjugates bilirubin?
uridine glucoronosyltransferase (UGT) catalyzes glucuronidation
most elevations in bili are the consequence of _____ liver disease (acquired/genetic)
acquired
isolated hyperbilirubinemia is often due to ____ conditions
genetic
name 3 inherited unconjugated hyperbilirubinemias
Gilbert’s Syndrome; Crigler-Najjar syndrome (Types I and II)
name 2 inherited conjugated hyperbilirubinemias
Dubin-Johnson syndrome; Rotor syndrome
when conj bili is significantly elevated in the plasma, a portion becomes?
covalently bound to albumin
the fraction of conj bili bound to albumin is referred to as _______
bilirubin delta
what is significant about bilirubin delta?
it has the same half-life as albumin (20 days) and thus it remains in the serum long after levels of other bili have dropped down to normal levels
total bili (tBili) includes?
Bu + Bc + Bd
direct bilirubin is a measure of?
Bc + Bd (technically) but usually just Bc because Bd is so low
indirect bili is a measure of?
unconjugated bilirubin
what are the three etiologic categories of jaundice?
pre-hepatic, hepatocellular, and obstructive
pre-hepatic jaundice results in increased ___ bili and is usually cause by?
unconjugated; hemolysis with overproduction of bili
what leads to the formation of black pigmented gallstones made of calcium bilirubinate?
chronic hemolysis, such as in sickle cell
with hemolytic anemia, what will be the color of the urine?
unconj bili does not appear in the urine, so it will be normal colored
hepatocellular jaudice results in increased ____ bili and is commonly caused by?
Bc and Bu; drug-induced or viral hepatitis
what color will the urine be with hepatocellular jaundice?
could be enough Bc to darken the urine
obstructive jaundice results in high levels of ____ and is caused by?
Bc; gallstone migrating out of gallbladder and lodging in common bile duct
what color is the urine in obstructive jaudice
can become very dark
what color will stool be in obstructive jaundice?
pale or clay-colored (normal color of stool comes from bili metabolites)
will urine contain urobilinogens?
NO, bili is not reaching the GI tract and thus no microbial metabolism occurs
elevated serum levels of aminotransferases reflect?
increased enzyme release due to liver cell injury or death
____ is specific for liver injury, while ____ may be elevated in muscle and heart disease as well
ALT; AST
if both ALT and AST are elevated, then there is most likely?
hepatocellular necrosis
do normal levels of AST/ALT exclude chronic liver disease?
NO; advanced cirrhosis can actually case decreased ALT synthesis
in what condition might aminotransferase levels fluctuate over time?
chronic hep C
alcoholic hepatitis often has an AST:ALT ratio of
greater than 2
when might you see aminotransferase levels in the 5-10 thousand range?
severe liver injury, such as tylenol OD, ischemia, herpes, or shock liver
which diseases show only mildly elevated aminotransferases?
chronic viral hepatitis, alcoholic and non-alcoholic steatohepatitis
what stimulates AP synthesis?
biliary tract obstruction, increased pressure in biliary system, and elevated concentrations of bile acids
other than hepatocytes and the canalicular membrane, where else is AP found?
bone, placenta
if AP levels are disproportionately high compared to bili, what should be considered?
granulomatous disorders or infiltrative lesions
if AP levels are super high compared to aminotransferases (and often bili), consider?
primary biliary cirrhosis, primary sclerosing cholangitis
how do you determine that elevated AP is of hepatic origin?
gamma-glutamyltransferase (GGT)
elevated GGT is highly _____, but not very _____ (SN, SP)
high sensitivity, low specificity
GGT may also be used as an indicator of?
alcohol abuse (a decrease during abstinence is especially indicative)
what degree of liver injury must occur in order to detect decreased synthesis of albumin or coag factors?
significant! There is a large reserve capacity
serum albumin levels reflect ____ synthetic dysfnc, while coag factors reflect _____ dysfnc (chronic, acute)
albumin = chronic; coag = acute and chronic
albumin levels are a marker of?
decompensation and prognosis in cirrhosis (but neither sensitive or specific)
in addition to chronic liver dz, hypoalbuminemia can result from?
protein loss (nephrotic syndrome, burns)
hypoalbuminemia in decompensated cirrhosis is due to reduced hepatic synthesis, as well as?
“third spacing” (edema, ascites)
prothrombin time assesses the ____ pathways of coagulation
extrinsic (all produced by the liver)
liver injury results in ____ changes in PT (rapid, slow)
rapid
an isolated modest elevation in GGT is likely due to?
alcohol consumption or medications
an isolated modest elevation in tBili is likely due to?
hemolysis
what lab findings would support choledocholithiasis?
very high tBili, elevated GGT and AP, mildly elevated ALT and AST (ALT > AST)
an AST more than 2x the ALT suggests?
alcoholic hepatitis
elevated AP and GGT alone suggest?
early primary biliary cirrhosis (or multiple liver mets)
low serum albumin and increased PT suggest?
chronic liver dysfunction
an isolated elevation in AP is indicative of?
bone disease or end of pregnancy
acute liver injury results in what lab findings?
super high AST & ALT, very high tBili and significantly prolonged PT
