Liver function tests Flashcards

1
Q

LFTs can be split into markers of liver cell damage and markers of synthetic function

Give examples of both

A

Liver cell damage:
- ALT, AST, ALK phosp, GGT, Bilirubin

Synthetic function:
- Clotting INR, Albumin, Glucose

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2
Q

What is the best marker of liver function in acute liver injury?

A

Prothrombin time

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3
Q

What LFTs are seen in **acute **viral hepatitis or paracetamol overdose or ischaemic hit?

Anything very acute

A

Transaminitis in the 1000s

(AST and ALT)

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4
Q

What does this ratio indicate:
ALT>AST?

A

Chronic liver disease e.g. NASH, chronic hep C, advanced cirrhosis

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5
Q

What is AST:ALT ratio of 2:1 indicating?

A

Alcoholic liver disease

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6
Q

Why is AST higher than ALT in alcoholic liver disease?

A

Alcohol metabolism affects the mitochondria of hepatocytes, this is where AST is more concentrated

GGT is also quite elevated in alcholic liver disease

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7
Q

What does a ratio of AST:ALT 1:1 indicative of?

A

Viral hepatitis

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8
Q

What does raised GGT and ALP indicate?

A

Cholestatic / obstructive picture

Also chronic alcoholic disease

ALP found in in bile duct epithelium

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9
Q

Raised ALP + Raised Bilirubin → ?

Raised ALP + Normal Bilirubin → ?

A

Raised ALP + Raised Bilirubin → Suggests obstructive jaundice.

Raised ALP + Normal Bilirubin → Consider early cholestasis, bone disease, or pregnancy.

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10
Q

Raised ALP + Raised GGT → ?

Raised ALP + Normal GGT → ?

A

Raised ALP + Raised GGT → Cholestasis (biliary obstruction, PBC, PSC, drug-induced).

Raised ALP + Normal GGT → Consider bone pathology.

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11
Q

ALP isolated rise which is >5x the normal upper limit

A

Bone = pagets disease
osteomalacia
Liver = cirrhosis

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12
Q

ALP isolated rise which is <5x the normal upper limit

A

Bone = primary tumour e.g. sarcoma, fracture

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13
Q

Why is ALP normal in myeloma?

A

Plasma cells suppress osteoblasts, alp is hence normal

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14
Q

Why may albumin be low?

A

Chronic liver disease
Malnutrition
protein losing enteropathy
sepsis - 3rd spacing
nephrotic syndrome

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15
Q

Why may urea be low?

A

Severe liver disease, malnutrition, pregnancy

because urea is made in liver

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16
Q

Raised urea x10 of upper limit?

A

Upper GI bleed (or large protein meal)

Dehydration / aki (as urea is excreted renally)

17
Q

How much albumin is normally synthesised?

A

200mg/g

hypoalbuminaemia is common in acute/systemically ill patients in hispital. Poor prognostic factor

18
Q

INR vs PT time?

A

INR is the PT time standardised for age and population

19
Q

What is bilirubin?

A

Breakdown product of heme, elevated levels manifest as yellowing (jaundice)

20
Q

What is the normal metabolism of bilirubin?

A

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

21
Q

What are prehepatic causes of jaundice?

A

Haemolytic anaemia

Ineffective erythropoiesis e.g. thalassemia

Congestive cardiac failure

22
Q

What are hepatic causes of jaundice?

A

Hepatocellular dysfunction

Impaired conjugation / Bilirubin update

Gilbert syndrome / crigler najjar syndrome

23
Q

What are post hepatic causes of jaundice?

A

Intraluminal obstruction e.g. stones / strictures

Luminal obstruction e.g. mass / neoplasms / inflammation

Dextra-luminal e.g. pancreas / cholangio carcinoma

24
Q

Prehaptic causes of jaundice

  • Conjugated/Un
  • urobilinogen
  • Urine bilirubin
  • urine colour
  • stool colour
  • AST/ALT
  • ALP
  • Splenomegaly
A
  • Unconjugated
  • urobilinogen increased
  • Urine bilirubin absent
  • urine colour normal
  • stool colour normal
  • AST/ALT normal
  • ALP normal
  • Splenomegaly present
25
Q

Hepatic causes of jaundice

  • Conjugated/Un
  • urobilinogen
  • Urine bilirubin
  • urine colour
  • stool colour
  • AST/ALT
  • ALP
  • Splenomegaly
A
  • Conjugated increased
  • Unconjugated increased
  • urobilinogen increased
  • Urine bilirubin present
  • urine colour dark
  • stool colour pale
  • AST/ALT increased
  • ALP increased
  • Splenomegaly present
26
Q

Post Hepatic causes of jaundice

  • Conjugated/Un
  • urobilinogen
  • Urine bilirubin
  • urine colour
  • stool colour
  • AST/ALT
  • ALP
  • Splenomegaly
A
  • Conjugated increased
  • urobilinogen decreased
  • Urine bilirubin present
  • urine colour dark
  • stool colour pale
  • AST/ALT increased
  • ALP increased!
  • Splenomegaly absent
27
Q

Why is there no bilirubin in urine for prehepatic jaundice causes?

A

There is unconjugated bilirubin tightly bound to albumin - cannot get through glomerulus

28
Q

Why is post hepatic jaundice present with dark urine and pale faeces?

A

increase in conjugated bilirubin ends up in blood rather than going through GI. Excreted by kidneys but no stercobilinogen so pale faeces

29
Q

Hepatomegaly with smooth margin may be seen in?

A

Viral hepatitis
Biliary tree obstruction
hepatic congestion 2 to HF

30
Q

Hepatomegaly with craggy border seen in?

A

Hepatic metastatic disease
Polycystic disease
Cirrhosis

31
Q

What would be see in wilson’s disease?

A

Isolated increase in unconjugated bilirubin

32
Q

What would be seen in Obstetric cholestasis?

A

Bilirubin 100+
Raised ALT, AST, GGT
Bile salts 10+