W2: Liver Flashcards
hepatic portal vein role
to take nutrients absorbed from small intestine to liver to be processed
what are rbcs broken down into + by what
heme + globin
by macrophages
heme broken down into
bilirubin + iron
how is bilirubin transported by the liver + why
bound to albumin - to incr its solubility
what makes urine yellow + faeces brown
urine converted to urobilin
faeces converted into stercobilinogen
7 liver functions
- Catabolism + excretion of bilirubin
- Mainten. of glucose homeostasis
- Metabolism of cholesterol + triacylglycerols
- Prod of some clotting factors
- Detoxification of drugs
- Catabolism of ‘amino’ (NH2) groups of AAs to urea
- Protein syn: albumin & globulins (except immunoglobulins)
3 tests for liver damage + how its indicated
indicated by high levels of:
- ALT (alanine aminotransferase)
- AST (aspartate aminotransferase)
- ALP (alkaline phosphatase)
bc when damaged they leak out into blood
3 liver function tests
- Total bilirubin
- Albumin
- GGT (gamma glutamyl transpeptidase)
3 strictly liver function tests
- Bilirubin
- Albumin
- Prothrombin time (clotting test)
what are ALT + AST + when are they abundant
Enzymes involved in the transfer of amino groups. Important in AA metabolism.
Correct name = aminotransferases
ALT & AST abundant in hepatocytes
AST also abundant in skeletal muscle cells + rbcs
Released into bloodstream when hepatocytes are damaged
ALP: found where, function, isoenzymes found in which organs, enzyme blood levels incr when
- enzyme found in hepatocyte mems close to bilary ducts
- function not fully understood
- isoenzymes in; liver, bone, intestines, placenta
-incr when pressure inside bilary ducts incr
GGT: found where, function, enzyme blood levels inc rwhen
- enzyme found in hepatocyte mems close to bilary ducts
- transfers gamma-glutamyl groups btwn peptides
- when pressure inside bilary duct incr
OR - when enzyme syn induced by: alc/ some antiepileptic drugs
albumin: synth where, carrier of, function,
- liver
- proteins, peps, drugs in blood
- maintains oncotic pressure in blood vessels
high or low conc of serum albumin in severe liver disease
low
low albumin suggests…
patient has disease but not specific enough to identify which
further testing needed
bilirubin: conjugated in liver with, excreted in,
- glucuronic acid
- bile
lab measures ___ bilirubin (adults)
normal values unconjugated vs conjugated
- total
uncon: 98%
con: 2%
prothrombin time
- clotting test: assesses clotting factors syn by liver
- gives an international normalised ratio (INR)
- prolonged clotting time in moderate/severe liver disease
ammonia: measured + not measured in
- only in neonates w severe illness, irritability, low consciousness level
-Not measured in adults w liver disease as levels do not correlate w severity of disease
glucose high or low in severe liver disease
low
main categories of liver disease
- hepatitis
- cholestasis
-mixed hep + chole - tumours + other infiltrative diseases
- alcohol liver disease
what does hepatitis + cholestasis mean
hep = inflamm of liver
cholestasis = bile flow impairment
infectious types of hepatitis
A, B, C
acute or chronic
other viruses - Epstein Barr virus causing glandular fever 9mild hep)
2 drugs/ toxins that can cause hep
alc
para overdose
2 other causes of hep
autoimmune
ischaemic - secondary to acute shock (causes rapid drop to BP)
ALT & AST usually x 20-50 ULN indictates
- acute hepatitis types A, B, C,
- secondary to severe ischaemia
- severe paracetamol overdose/ other overdoses
ALT & AST x 2 -10 ULN indicates
- glandular fever, autoimmune hepatitis & chronic hepatitis
other abnormalities
incr serum ALP 2 x ULN
incr serum bilirubin (depends on severity)
Usually 3-4 x ULN
In severe cases, jaundice appears (usually bilirubin > 4-5 x ULN)
Both unconjugated and conjugated
other abnormalities (2)
Bilirubin appears in urine (brown colour). Not normally present
Clotting may be impaired. incr INR (depends on severity)
effects of massive hep (fulminant)
- Hypoglycaemia
- Hypoalbuminaemia
- Severe clotting impairment
- V high bilirubin
- Extremely high ALT & AST
- V high ammonia -> altered level of consciousness
what is urgently given to prevent liver damage after paracetamol overdose
N-acetylcysteine
where can cholestasis occur
anywhere from liver canaliculus to duodenum
2 types of obstruction + examples
partial or complete
gall stones
extra-hepatic cancer causing obstruction (pancreas) which
presses on bile duct so bile can’t be removed from liver
(cholestasis can be caused by other diseases affecting billary tree)
how is cholestasis detected?
cholestatic pattern
- incr back-pressure on cells of canaliculi + then hepatocytes
- big incr ALP (depends on severity)
Twice ULN – 20 x ULN
- ALT & AST slightly raised (but can be 3-4 x ULN)
- big incr bilirubin 5 – 15 x ULN, 95% conjugated
- bilirubin appears in urine (brown colour) not normally present
how is complete obstruction cholestasis detected
stool is pale as bile pigments don’t reach gut
what is mixed hepatitis/ cholestasis
damage to both hepatocytes + cells of bile duct
causes of mixed hep/chole
During sepsis
Drugs - immunosuppressants
Autoimmune liver disease
Any hepatic/ cholestatic disorder already mentioned
effect of mixed H+C on aminotransferases + ALP
mildly-moderately raised
indicator of autoimmune hep
- incr antinuclear antibodies (Abs that bind to nucleus of own cells)
- incr smooth muscle antibodies
types of liver tumours
- Benign or malignant
- Single or multiple nodules/masses. Usually infiltrative
- Primary or secondary (metastases from tumour in different part of body)
in liver function test there’s big incr in which enzyme to detect advanced liver cancer
ALP
what’s raised in hepatocarcinoma
alpha-feto-protein (AFP) as this is prod by tumour in liver of foetus
effects of chronic alc intake on GGT + red cell vol
- incr GGT due to incr enzyme syn
- incr red cell vol (macrocytosis)
how long for GGT to go back to normal if individual stops alc intake
3-4 weeks
disadvs of GGT testing
- not sensitive
- not specific as levels of GGT can be incr in most types of liver disease
Other consequences of chronic alcohol intake
- Fatty liver: deposition of fat in liver, associated w raised serum triaylglycerols -> (not damaging but can lead to) inflamm of liver, fibrosis of liver -> liver cancer
- Raised plasma urate
- Acute hepatitis (acute alcohol intake)
- Liver cirrhosis (fibrosis of the liver) in heavy drinkers. Can progress to malignancy.
why does MCV take longer to normalise
bc rbc half life = 120days
