Liver function tests Flashcards
LFTs can be split into markers of liver cell damage and markers of synthetic function
Give examples of both
Liver cell damage:
- ALT, AST, ALK phosp, GGT, Bilirubin
Synthetic function:
- Clotting INR, Albumin, Glucose
What is the best marker of liver function in acute liver injury?
Prothrombin time
What LFTs are seen in **acute **viral hepatitis or paracetamol overdose or ischaemic hit?
Anything very acute
Transaminitis in the 1000s
(AST and ALT)
What does this ratio indicate:
ALT>AST?
Chronic liver disease e.g. NASH, chronic hep C, advanced cirrhosis
What is AST:ALT ratio of 2:1 indicating?
Alcoholic liver disease
Why is AST higher than ALT in alcoholic liver disease?
Alcohol metabolism affects the mitochondria of hepatocytes, this is where AST is more concentrated
GGT is also quite elevated in alcholic liver disease
What does a ratio of AST:ALT 1:1 indicative of?
Viral hepatitis
What does raised GGT and ALP indicate?
Cholestatic / obstructive picture
Also chronic alcoholic disease
ALP found in in bile duct epithelium
Raised ALP + Raised Bilirubin → ?
Raised ALP + Normal Bilirubin → ?
Raised ALP + Raised Bilirubin → Suggests obstructive jaundice.
Raised ALP + Normal Bilirubin → Consider early cholestasis, bone disease, or pregnancy.
Raised ALP + Raised GGT → ?
Raised ALP + Normal GGT → ?
Raised ALP + Raised GGT → Cholestasis (biliary obstruction, PBC, PSC, drug-induced).
Raised ALP + Normal GGT → Consider bone pathology.
ALP isolated rise which is >5x the normal upper limit
Bone = pagets disease
osteomalacia
Liver = cirrhosis
ALP isolated rise which is <5x the normal upper limit
Bone = primary tumour e.g. sarcoma, fracture
Why is ALP normal in myeloma?
Plasma cells suppress osteoblasts, alp is hence normal
Why may albumin be low?
Chronic liver disease
Malnutrition
protein losing enteropathy
sepsis - 3rd spacing
nephrotic syndrome
Why may urea be low?
Severe liver disease, malnutrition, pregnancy
because urea is made in liver
Raised urea x10 of upper limit?
Upper GI bleed (or large protein meal)
Dehydration / aki (as urea is excreted renally)
How much albumin is normally synthesised?
200mg/g
hypoalbuminaemia is common in acute/systemically ill patients in hispital. Poor prognostic factor
INR vs PT time?
INR is the PT time standardised for age and population
What is bilirubin?
Breakdown product of heme, elevated levels manifest as yellowing (jaundice)
What is the normal metabolism of bilirubin?
Conjugation in hepatocytes and subsequent secretion into bile duct -> GI tract -> metabilised in GI into urobillinogen
Urobilinogen excreted by kidneys as urobilin, rest is converted to stercobilin in faeces
What are prehepatic causes of jaundice?
Haemolytic anaemia
Ineffective erythropoiesis e.g. thalassemia
Congestive cardiac failure
What are hepatic causes of jaundice?
Hepatocellular dysfunction
Impaired conjugation / Bilirubin update
Gilbert syndrome / crigler najjar syndrome
What are post hepatic causes of jaundice?
Intraluminal obstruction e.g. stones / strictures
Luminal obstruction e.g. mass / neoplasms / inflammation
Dextra-luminal e.g. pancreas / cholangio carcinoma
Prehaptic causes of jaundice
- Conjugated/Un
- urobilinogen
- Urine bilirubin
- urine colour
- stool colour
- AST/ALT
- ALP
- Splenomegaly
- Unconjugated
- urobilinogen increased
- Urine bilirubin absent
- urine colour normal
- stool colour normal
- AST/ALT normal
- ALP normal
- Splenomegaly present
