Clinical Interpretation Of Abnormal Liver Function Tests Flashcards
What are biochemical markers for liver disease?
- *Aminotranserases
- AST
- ALT
**Alkaline phosphatase
5’-nucleotidase
**Gamma-glutamyl transpeptidase (GGT)
**Lactate dehydrogenase (LDH)
**Bilirubin
** = most common
What are biosynthetic liver function test enzymes (LFTs)
Bilirubin
Prothrombin time (PT/INR) - coagulation factors 2/5/7/10
Albumin
Immunoglobulins (IgG/IgM/IgA)
Conjugated bilirubin excretion
Are liver function tests and enzyme levels sensative and specific for certain GI diseases?
NO
- they only work to help narrow down
- they can be normal in serious illness or elevated in normal liver functions
What are the two common enzyme elevation patterns?
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
What is the R-value?
(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
ALT vs AST ratios
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
Relationship between alkaline phosphatase and GGT enzyme relationships
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
Direct vs indirect bilirubin
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)
What are possible immunoglobulins and auto-antibodies associated with liver diseases?
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
What does ALT/AST levels >500 usually imply?
A acute serious hepatocellular necrosis process
-usually viral infection/direct toxin induction or ischemia
alkaline phosphatase and albumin is normal
What does alkaline phosphatase levels >4x normal usually imply?
Cholestatis or obstructive disease
What is the normal liver size?
7-10 cm for women
- 5-12.5cm for men
* anything higher = hepatomegaly*
Can chronic liver diseases cause gynenomastea in men?
Yes
How to tell cholestasis apart from cholecystitis?
Cholesystitis will show a fever and leukocytosis On labs
also cholecysttis pain usually presents with Murphy sign