LIVER FUNCTION TESTS

Question 1

LIVER FUNCTION TESTS

Answer 1

ASPARTATE AMINOTRANSFERASE (AST)/ ALANINE AMINOTRANSFERASE (ALT)

Increases with hepatocellular necrosis / inflammation

ALT more sp

AST: heart (MI), skeletal muscle, kidney, brain, RBC / WBC. AST/ALT > 5, suggests the injury is extrahepatic in origin

BILIRUBIN

Product of heme metabolism.

Elevated unconjugated:
hemolysis
enzyme (Crigler-Najjar, Gilbert’s)

Elevated conjugated:
cholestasis
enzyme (Dubin-Johson, Rotor’s)

ALKALINE PHOSPHATASE

Enzyme bound in hepatic canalicular membrane

Increased with biliary obstruction or intrahepatic cholestasis

DDx: Bone, Liver, intestines, kidney, placenta.

Get GGT to confirm hepatic origin

LIVER FUNCTION TESTS

Albumin: decreases slowly in liver failure

Prothrombin Time: Increases quickly in liver failure.

Question 2

MANAGEMENT

Answer 2

INVESTIGATIONS: HEPATOCELLULAR INJURY

Acetaminophen Level

EtOH Level

HBV and HCV Serology

Liver U/S with Doppler

Consider: Iron studies, ANA, ASMA, Ig levels, ceruloplasmin

INVESTIGATIONS: CHOLESTASIS

RUQ U/S to assess for ductal dilation

INVESTIGATIONS: INFILTRATIVE
GGT (to ensure ALP is from liver source)
RUQ U/S
OR
CT

Question 3

COMMON LIVER FUNCTION TEST ABNORMALITY PATTERNS

Answer 3

HEPATOCELLULAR INJURY LFT PATTERN
++AST ++ALT
+/-ALP +/- Bili

10 x ELEVATION OF AST / ALT:
Acute Viral Hepatitis
Ischemic Injury
Acetaminophen Toxicity
Mushroom Poisoning (amanita phalloides)

5-10 x ELEVATION AST / ALT
Alcoholic hepatitis (Typically AST/ALT > 2)
Rhabdomyolysis

< 5 x ELEVATION AST / ALT
Non-alcoholic fatty liver disease (MCC)
Alcohol induced liver injury (Typically AST/ALT > 2)
Resolving hepatic diseases
Drug induced liver injury

CHOLESTASIS LFT PATTERN:
++ALP ++ Bili
+/-AST +/-ALT

ALP + Bili ELEVATION:

Obstructing stone in common duct
+Dilated common bile duct > 6 mm

ALP + Bili + AST/ALT ELEVATION:

Severe obstruction of common duct (choledocholithiasis) with ascending infection (cholangitis)

sensitivity and specificity for elevated bilirubin were 0.84 and 0.91, and for elevated alkaline phosphatase were 0.92 and 0.79
sensitivity and specificity for ultrasound were 0.73 and 0.91

CONJUGATED Bili ELEVATION:

Common or intrahepatic biliary duct obstruction

UNCONJUGATED BIli ELEVATION:

Hemolysis
INFILTRATIVE LFT PATTERN:

++ALP
Near normal Bili, AST, ALT

Question 4

DDX: HEPATOCELLULAR INJURY (COMMON CAUSES)

Answer 4

EtOH
Acetaminophen

HBV
HCV

Autoimmune

Hemochromatosis
a1-AT Deficiency
Wilson’s

NAFLD
Ischemic
Congestive (CHF)
Budd-Chiari

Question 5

DDX: CHOLESTATSIS

Answer 5

DUCTAL DILATION: CBD > 6 mm
Biliary Obstruction:
Choledocholithiasis
Cholangiocarcinoma
Pancreatic Cancer
Sclerosing Cholangitis

NO DUCTAL DILATION:
Intrahepatic Cholestasis:
TPN
Sepsis
Post-Op
PBC

Biliary Epithelial Damage:
Hepatitis
Cirrhosis

Question 6

DDX: INFILTRATIVE

Answer 6

Malignancy
Granulomas
Abscess