DSA 2: Elevated Liver Enzymes Flashcards
what are the lab tests for liver
chemistry tests- markers of liver damage: AST/ALT, ALP, bilirubin, LDH & GGT
true liver fxn: PT/INR, Albumin, Cholesterol, Ammonia
what are characteristics of hepatocellular dz
primary injury is to hepatocytes
primarily AST/ALT elevation (> than ALP levels)
ALT more specific for liver than AST
What are characteristics of cholestatic dz
primary injury is to the bile duct
ALP & bilirubin elevated (> AST/ALT) - failure of bile to reach duodenum, jaundice & pruritis, pure cholestasis
what do bilirubin tests show
indication of hepatic uptake, metabolic (conjugation) and excretory functions [fractionate to get conjugated vs unconjugated]
What information do aminotransferase (transaminases) reveal
= AST & ALT
highest in hepatocellular necrosis (e.g., viral hepatitis, toxic or ischemic liver injury, acute hepatic vein obstruction)
occasionally with sudden, complete biliary obstruction (e.g., from gallstone)
ALT more specific for liver injury, bc AST also in striated M and other organs
EtOH-induced liver injury - modest increase w/ more prominent elevation of AST than ALT (2:1)
what information do ALP reveal
Sensitive indicator of cholestasis, biliary obstruction (enzyme increases more quickly than serum bilirubin) & liver infiltration
Elevations - nl childhood, pregnancy, and bone dz
Tissue-specific isoenzymes can be distinguished by fractionation
what does GGT reveal
Correlate w/ serum ALP activity
increased –> THINK liver
Normal think other source (bone/placenta)
How do coagulation factors give info about liver function
use INR
-if above 1 and not on meds - is it liver dz?
all factors except factor VIII made in liver (which fxn only in presence of fat-soluble vit K)
single best acute measure of hepatic synthetic fxn
PT prolongation from fat malabs distinguished from hepatic dz by rapid & complete response to vit K replacement
What information does albumin reveal
chronic liver dz - degree of hypoalbuminemia correlates w/ severity of liver dysfxn
decreased w/ decreased hepatic synthesis (chronic liver dz or prolonged malnutrition); excess loss in urine/stool
insensitive indicator of acute hepatic dysfxn
What do ammonia levels reveal
elevation of blood ammonia DOES NOT correlate w/ hepatic fxn or the presence or degree of acute encephalopathy
what are nonhepatic sources of common liver tests
what are the direct/indirect-reacting bilirubin levels and associated features of
liver dz
hemolysis
gilbert syndrome
