Clinical Interpretation Of Abnormal Liver Function Tests

Question 1

What are biochemical markers for liver disease?

Answer 1

• *Aminotranserases
• AST
• ALT

**Alkaline phosphatase

5’-nucleotidase

**Gamma-glutamyl transpeptidase (GGT)

**Lactate dehydrogenase (LDH)

**Bilirubin

** = most common

Question 2

What are biosynthetic liver function test enzymes (LFTs)

Answer 2

Bilirubin

Prothrombin time (PT/INR) 
- coagulation factors 2/5/7/10

Albumin

Immunoglobulins (IgG/IgM/IgA)

Conjugated bilirubin excretion

Question 3

Are liver function tests and enzyme levels sensative and specific for certain GI diseases?

Answer 3

NO

• they only work to help narrow down
• they can be normal in serious illness or elevated in normal liver functions

Question 4

What are the two common enzyme elevation patterns?

Answer 4

1) hepatocellular damage is present
- elevated AST/ALT
- AST, ALT levels will both be higher than alkaline phosphatase
- bilirubin levels VARY (dont look at this)

2) cholestatic process (blockage of the gallbladder)
- elevated bilirubin, alkaline phosphate and CGT
- Alkaline phosphate > AST/ALT levels

3) isolated hyperbilirubinemia
- ONLY elevated bilirubin

Question 5

What is the R-value?

Answer 5

(measured ALT/ upper limit of normal ALT) / (measured alkaline phosphatase/ upper limit of alkaline phosphatase)

Helps narrow stuff down but hardly ever used

If > 5 = hepatocellular injury

If 2-5 = mixed pattern

If <2 = cholestatic injury

Question 6

ALT vs AST ratios

Answer 6

Helps determine potential causes of liver damage

ALT > AST = general hepatitis

AST > ALT = alcoholism or advanced liver cirrhosis

**ALT is found in hepatocyte cytosol

**AST is found in hepatocyte mitochondria

Question 7

Relationship between alkaline phosphatase and GGT enzyme relationships

Answer 7

If alkaline phosphatase and GGT are elevated = biliary issue

• either obstruction/infection (cholestasis/cholecystis)
• **total obstruction will not show this though (both enzymes might be normal)

If alkaline phosphatase is elevated but GGT is normal = bone issue

Question 8

Direct vs indirect bilirubin

Answer 8

Direct (conjugated)

• is water soluble And polar
• seen in urine
• already processed new bilirubin
• is elevated with biliary obstruction or specific hepatocellular diseases

Indirect (unconjugated)

• is lipid soluble and non-polar
• not seen in urine, only blood
• non processed old bilirubin
• elevated with hemolysis or general hepatic diseases (hepatitis)

Question 9

What are possible immunoglobulins and auto-antibodies associated with liver diseases?

Answer 9

IgG elevation = autoimmune hepatitis (both type 1/2)

IgM elevation = primary biliary cirrhosis

IgA elevation = alcoholic abuse

IgA/M/G elevation = liver cirrhosis

ANA/ASM = auto immune hep type 1

LKM = auto immune hep type 2

AMA = primary biliary cirrhosis

ANCA = primary sclerosing cholangitis

Question 10

What does ALT/AST levels >500 usually imply?

Answer 10

A acute serious hepatocellular necrosis process
-usually viral infection/direct toxin induction or ischemia

alkaline phosphatase and albumin is normal

Question 11

What does alkaline phosphatase levels >4x normal usually imply?

Answer 11

Cholestatis or obstructive disease

Question 12

What is the normal liver size?

Answer 12

7-10 cm for women

10. 5-12.5cm for men
    * anything higher = hepatomegaly*

Question 13

Can chronic liver diseases cause gynenomastea in men?

Answer 13

Yes

Question 14

How to tell cholestasis apart from cholecystitis?

Answer 14

Cholesystitis will show a fever and leukocytosis On labs

also cholecysttis pain usually presents with Murphy sign