Interpreting liver chemistries

Question 1

Liver chemistry abnormalities indicating hepatocellular damage

Answer 1

AST and ALT

Question 2

Liver chemistry abnormalities indicating cholestasis, impaired conjugation or biliary obstruction

Answer 2

bilirubin

Question 3

liver chemistry abnormalities indicating cholestasis, infiltrative disease, or biliary obstruction

Answer 3

alkaline phosphatase

Question 4

liver chemistry abnormalities indicating synthetic dysfunction

Answer 4

albumin, prothrombin time

Question 5

What does PT (prothrombin time) assess?

Answer 5

extrinsic clotting pathway

Question 6

prolonged PT

Answer 6

significant hepatocellular dysfunction, vitamin K deficiency

Question 7

role of AST/ALT aminotransferases

Answer 7

catalyze transfer of amino acid groups to form hepatic metabolites

Question 8

organs expressing AST

Answer 8

liver, heart, muscle, blood

Question 9

organs expressing ALT

Answer 9

liver only

Question 10

AST:ALT ratio > 2

Answer 10

suggests alcoholic liver disease.

preferential alcohol-induced injury to mitochondria enriched in AST

Question 11

Causes of severe ( > 15x normal) AST and ALT elevations

Answer 11

acute viral hepatitis, meds/toxins, ischemic hepatitis, autoimmune hepatitis, Wilson’s disease, acute Budd-Chiari syndrome, thrombosis

Question 12

alkaline phosphatase role

Answer 12

hydrolase –> removes phosphate groups from nucleotides, proteins and alkaloids

Question 13

causes of alk phos elevation

Answer 13

cholestatic/infiltrative diseases of liver, obstruction of biliary system, bone disease, pregnancy, chronic renal failure

Question 14

What lab is used to differentiate hepatobiliary vs nonhepatobiliary etiology for rise in alk phos?

Answer 14

5’ nucleotidase and

GGT: not present in bone. elevated in alcohol consumption and almost all types of liver disease

Question 15

infiltrating liver diseases –> high alk phos

Answer 15

sarcoidosis, tuberculosis, fungal infection, amyloid, lymphoma, metastasis, HCC

Question 16

process of bilirubin conjugation

Answer 16

unconjugated bilirubin in the sinusoids –> uptake to hepatocytes via oatp –> conjugation –> ATP pump of conjugated bilirubin into bile canaliculus

Question 17

mechanism of hemolytic jaundice

Answer 17

high levels of unconjugated bilirubin in the blood –> overwhelmed oatp –> unconjugated bilirubin cannot be completely taken up by hepatocytes –> rise in indirect bilirubin levels

Question 18

mechanism of biliary obstruction jaundice

Answer 18

conjugated bilirubin cannot exit canaliculus/duct –> shunt to blood –> rise in serum direct bilirubin levels

Question 19

Gilbert’s disease

Answer 19

stress-related hyperbilirubinemia (rise in indirect bilirubin)

Question 20

Crigler-Najjar syndrome

Answer 20

Autosomal recessive

Type 1 = absence of UDP-GT –> severe jaundice, neuro impairment

Question 21

Dubin-Johnson syndrome

Answer 21

defective secretion of conjugated bilirubin (mutated MRP2 in ATP binding region) –> elevated conjugated bilirubin

benign

Question 22

mechanism of bilirubin elevation in cirrhosis

Answer 22

increased fibrosis –> decreased unconjugated bilirubin into the hepatocytes –> rise in indirect bilirubin

increased hemolysis in severe liver disease