Interpreting liver function tests Flashcards
What are the main roles of the liver?
detoxification - metabolism and excretion of drugs
process and storage of - amino acids, proteins (most produced by the liver, except immunoglobulins), carbohydrate, cholesterol and vitamins
synthesis of bile acids -cholesterol catabolism
catabolic site for many of the hormones - insulin, glucagon, oestrogens, glucocorticoids, GH, PTH, conversion of VITd to 25-OHD
contribution to the immune response
What routine biochemical tests are there to assess liver function?
bilirubin hepatocellular enzymes - ALT (AST - less specific) hepatobiliary enzymes - ALP, gamma-GT albumin total protein
What clinical questions need to be asked when assessing the liver?
is the liver disease present?
what is the aetiology?
what is the severity?
can the disease be monitored?
What are the possible symptoms in which liver disease may present?
jaundice
abdo distension
ankle swelling - odema due to altered albumin
haemetemesis
pruritis
pale stools and dark urine - due to obstruction
What important factors should you ask about in the history if you suspect liver disease?
recent travel duration of illness drug use alcohol consumption family history weight loss BMI - fatty liver
What are the normal ranges for:
- total bilirubin
- ALP
- ALT
- AST
- Albumin
- gamma-GT (M and F)
- total bilirubin = <21 micromol/L
- ALP = 30-130 U/L = also found in bone and intestine, varying levels in adolescents
- ALT = 5-40 U/L
- AST = 5-43 U/L
- Albumin = 35-50g/L
- gamma-GT (M and F) = 9-50u/l and 9-40u/l
What is bilirubin a product of?
haem catabolism - 85% red cell precursors myoglobin cytochromes peroxidase daily production = 170-300 micromol/day
What are the different types of hyperbilirubinaemia?
pre-hepatic = haemolytic conditions cause raised bilirubin (unconjugated) but with no bilirubinaemia
hepatic = bilirubin (unconjugated and conjugated) is elevated at some stage of most hepatobiliary disease (with biliruburia)
post-hepatic = raised bilirubin (conjugated) due to bile outflow obstruction - bilirubinaemia
When is jaundice noticeable?
about 50 micromol/L
What are the main causes of pre-hepatic unconjugated hyperbilirubinaemia?
Production from haem
- haemolysis - hereditary, acquired or rapid turnover in neonates
Reduced delivery of unconjugated bilirubin in plasma
- R sided CCF, portocaval shunt
Reduced uptake of unconjugated bilirubin across liver membrane
- competitive inhibition e.g. drugs
- Gilbert’s (UGT1A1*28)
- Sepsis, fasting
What are the main causes of post-hepatic conjugated hyperbilirubinaemia?
Reduced secretion of conjugated bilirubin into the canaliculi
- hepatocellular disease - hepatitis, intrahepatic cholestasis
- drugs
Reduced drainage
- extrahepatic obstruction - stones, carcinoma, stricture, atresia
Sclerosing cholangitis intrahepatic obstruction
- drugs
- granuloma
- PBC
- tumour
What are the different types of jaundice?
haemolytic
cholestatic
hepatocellular
What criteria suggest haemolytic jaundice?
bilirubin usually <75 micromo/L no bilirubin in urine Reticulocytosis Reduced Hb Reduced haptoglobin LDH may increase
What criteria suggest cholestatic jaundice?
Bilirubin may be really increased
Bilirubin in urine
ALP > x3 ULN
AST, LDH and ALT moderately increased
What criteria suggest hepatocellular jaundice?
AST + ALT significantly increased
Bilirubin increased later
Bilirubin in urine
ALP raised later
What are the differences between AST/ALT and ALP/gamma-GT?
AST and ALT = cytosolic enzyme (50% AST is mitochondrial)
- increased with hepatic damage
ALP / gamma-GT = membrane bound glycoprotein enzyme
- increased with cholestatic damage
What happens to the enzymes in liver cell damage ?
AST released more quickly in liver disease
ALT more chronic release and may reflect length of disease
- fatty liver causes rises in ALT more often than AST
What happens to the enzymes in cholestasis ?
ALP increased
gamma-GT increased - can be induced by lots of alcohol
Alcohol and Gamma-GT
- increases are noted BUT increased gamma-GT is often found in pts with increased triglyceride and fatty liver, diabetes
Where is AST found?
in the liver - predominantly mitochondrial
in the muscle - predominantly cytoplasmic
in red blood cells - gross haemolysis
Where is ALT found?
cytoplasmic enxyme
Where is ALP found in ?
bone
placenta
growth phases in childhood and adolescence
when bone is remodelled (after fracture)
What are plasma proteins usually included in?
LFTs
- NOT specific
- albumin - hypoalbuminaemia very common in hospitalised patients
- immunoglobulinaemia can reflect liver disease- also a general indicator of chronic infection
What are some other examples of plasma proteins?
caeruloplasmin = reduced in wilson’s disease (problem with copper metabolism)
alpha-1 antitrypsin - protease inhibitor, deficiency states lead to liver/lung disease
coagulation proteins - short half life, use INR
What liver function test is used for liver tumours?
AFP (alpha-fetoprotein) 75% cases
What liver function tests are used for metabolic liver disease?
alpha-1 antitrypsin deficiency
haemochromatosis
iron, total iron binding capacity (transferrin) ferritin
Wilson’s disease - serum copper, caeruloplasmin
What is the AST:ALT ratio?
normal ration of AST to ALT = ABOUT 0.8
>1 = EVIDENCE OF CIRRHOSIS
What would you want to check if you suspected hepatocellular disease?
check transaminase > about 5xULN
ALP normal or slightly increased
What would you want to check if you suspected cholestatic disease?
ALP >200U/L
Transaminase normal or slightly raised <200U/L
If there was mixed liver disease what would you expect to see?
significant increases in ALP and transaminase
both greater than 200U/L
Case 1: - 24 F, no meds - mild jaundice, pallor, malaise, 6/12 hx heavy irregular menstrual periods - no spleno or hepatomegalu investigations: - TProt: 77g/l - Alb : 35g/L - ALP: 110U/L - ALT: 42 U/L - Bili: 48 umol/L
What are the differential diagnosis?
haemolytic disease
iron deficiency anaemia
gilbert’s syndroe
hepatobiliary disease
on futher testing:
- Tbil: 48
- Cbil: 11
- LDH: 149U/L (increased)
- Iron: 5 (decreased)
iron deficiency anaemia
What is gilbert’s syndrome?
autosomal dominant (7%) intermittant mild jaundice with unconjugated bilirubin periods of fasting and illness
Case 2: - 14 M treated for broken arm - mildly jaundiced - splenomegaly Investigations: - Tprot: 75 - Alb: 40 - ALP: 98 - ALT: 14 - Bili: 68 - Hb:10.3 - Cbil: <5 - LDH: 560U/L (increased) - haptoglobin: 0.1 (reduced)
What are the differential diagnoses?
unconjugated hyperbilirubinaemia, LDH and haptoglobin=> haemolytic process
hereditary spherocytosis
Case 3: - 35 F - 4/52 hx malaise, anorexia, upper abdo pain - dark urine - overt jaundice for 3/7 Investigations: - Tprot - 71 g/dl - Alb- 42 - ALP - 180 - GGT - 331 - ALT 2090 - AST 1788 - bilirubin - 126 What is the potential diagnosis?
Serology:
- hep A and C negative
- hep b positive
Case 4: - 65 M - AAA repair - after OP developed severe chest pain and shock - BP unrecordable - Acute MI INVESTIGATIONS: - T prot: 69 to 63 - ALP: 125 to 13 - GGT: 50 to 169 - ALT: 43 to 955 - AST: 30 to 812 - Bili: 14 to 17 Rapid development of hepatocellular damaage, no jaundice and hypoxic damage to liver What are the main causes of acute hepatocellular damage?
hypoxia
chemicals
drugs
acute hepatitis
Case 5: - 49 F - pneumonia and septicaemia - started on erythromycin and 5 days later become jaundiced and complained of pruritis - no pain investigations: - TProt: 72 to 69 -ALP: 120 to 328 - GGT: 43 to 402 - ALT: 24 to 67 - AST: 30 TO 89 - Bili:13 to 156
What is the diagnosis?
Erythromycin associated cholestasis
re-challenge the patient when LFTs have normalised
stopped it and when back to normal
What is the classical picture of obstructive jaundice?
significantly elevated ALP with mild elevations of transaminase
stone in common bile duct
