Lecture 12- Jaundice and liver function tests (LFTs) Flashcards
Jaundice
= clinical manifestation of increase bilirubin the blood
- Yellow discolouration of sclera and the skin
- When Hb goes to the Spleen it is broken down into haem and globin
*
- Globin
- Haem
haem metabolism
- Converted to biliverdin (unconjugated)
- Transported via albumin to the liver
- Liver conjugates bilirubin with glucuronic acid to make it water soluble
- Can enter entero- hepatic circulation
- Can travel down to duodenum and stay in the gut à oxidised to stercobilin – makes faecal matter brown
- Can go to the kidney and be excreted as urobilinogen
causes of jaundice
- pre-hepatic
- hepatic
- post-hepatic
pre-hepatic jaundice
- Too much break down of HB –> haem
- Too much demand for liver
- Liver cant conjugate it all
- Therefore some bilirubin is unconjugated
what can cause increased breakdown of Hb
- Haemaglobinopathies
- Sickle cell
- Thalamasemia
- Spherocytosis
- Haemolysis
hepatic jaundice
- Liver function down (reduced hepatocyte function)
- Reduced conjugating ability of the liver
causes of hepatic jaundice
Chronic liver disease
Acute liver damage
post hepatic jaundice
- Any obstructive condition to the bile duct à if any part of excretion pathway is obstructed e.g. gall stones
- Most common
which type of bilirubin (conjugated or unconjugated) will be raised if cause is post-hepatic
- Type of bilirubin likely to be raised is conjugated –> water soluble –> goes through blood stream to the kidney
- More bilirubin excreted by the kidney
- Therefore discolouration of the urine
- Dark urine, pale stools
post hepatic causes
- Gall stones
- Inflammation which causes scarring or narrowing of the biliary tree
- Enlargement of the head of the pancreas (pancreatic carcinoma)à painless jaundice (red flag)
- Intrahepatic obstruction within the liver
- Inflammation/ oedema
- Tumour e.g. hepatocellular carcinoma (compression locally)
- Cirrhosis- no expansile
- Compresses veins – portal hypertension
- Also compresses bile ducts in liver
what is included in a liver function test
- albumin
- ALT
- AST
- ALO
- Bilirubin
albumin levels represent
synthetic function of the kidney
- can have renal causes too
damage to the liver causes an increase in which enzymes being released into the plasma
ALT
AST
ALT
- More specific to liver ‘L’
- Acute liver damage (likely for them both to go up)
- AST
-
Aspartate transaminase
- Also found in cardiac (increased troponin) and skeletal muscle (look at increase in CK) and RBC (FBC)
- Chronic liver damage (likely for them both to go up)
- ALP- alkaline phosphatase
- Bile ducts in the liver blocked (cholestasis)
- Can be high in children that are growing quickly/ also malignancy of bone
- Gamma-glutamyl transferase - another enzyme which will confirm if the raised ALP are caused by a damaged or obstructed bile duct as opposed to the bone
- Bilirubin
-
Conjugated vs unconjugated
- Unconjugated
- Neonatal jaundice
- Unconjugated bilirubin can cross the BBB
- Damage to the brain
- Unconjugated
Indications for LFTs
- Healthy (baseline LFTS)
- Liver conditions (monitor)
- Suspected liver pathology
e.g. Women with abdominal pain and looks jaundiced. Ultrasound shows obstructed CBD
- Post-hepatic jaundice
- Obstructive pattern on LFT
e.g. Man with vomiting and jaundice
- Acute vital hepatitis
- Hepatic jaundice
- Hepatocellular damage on LFTs
- Must be pre-hepatic
- Increased unconjugated bilirubin (abnormality in red blood cells –> look at FBC e.g. haemolytic anaemia)
if increase in uncongugated bilirubin
must be pre-hepatic cause
- would be hepatic of post-hepatic if conjugated
e.g. Paracetamol overdose
- Hepatocellular damage indicated by high AST/ALT
- Hepatic cause
e.g. Severe epigastric pain and vomiting
- Common bile duct obstruction
- Stone obstruction after pancreatic duct
- ALP will be high due to damage to bile duct cells
increased ALP indicates
obstructive pattern- gall stones
e.g. no sign of jaundice
- Obstructive pattern but no jaundice yet
e.g. mixed picture
- Think of the clinical picture
- Some liver problems can show a mixed picture
- Hepatocellular (cancer can cause direct damage to hepatocytes) and obstructive damage (cause compression to bile duct cells)
- Both hepatic and post-hepatic causes
- GI cancer has metastasises to the liver (most common cause of this mixed picture)
What clinical signs might be evident if the Liver is unable to synthesise Albumin?
oedema–> ascites
In basic terms why might someone with Liver disease become confused?
build up of ammonia which is toxic to the brain
In simple terms what is thought to be the aetiology of Non- alcoholic fatty liver disease (NAFLD)?
insulin resistance increase the amount of glucose converted to TAF
- deposited in the liver
In simple terms what is thought to be the aetiology of Non- alcoholic fatty liver disease (NAFLD)?
wilsons
In basic terms, how is the Portal circulation different to the Systemic circulation?
goes through the liver
What potential complications of portal hypertension can result in haematemesis?
oesophageal varices
What duct is formed when the right and left hepatic ducts join as they exit the Liver?
common hepatic duct
In simple terms, what is the underlying problem in prehepatic jaundice
higher breakdown of haem
related to high amount of billirubin
too much for the liver to conjugate
mixed conjugated and unconjugated billirubin in blood test
What classification of hyperbilirubinaemia do you get in Hepatic jaundice?
hepatic and post-hepatic
State two common causes for Post-Hepatic jaundice
gall stones
strictures of biliary tree
What might a patient notice about the colour of their faeces if
they have Post-Hepatic jaundice?
pale
What measurement included in Liver Function Tests actually measures Liver function
ALT- most specific to hepatocellular damage
Following contraction of the gallbladder, what structures does Bile pass through on its journey to the duodenum?
common bile duct and ampulla of vater into the 2nd part of the duodenum
Briefly describe the potential effects of excess alcohol on the Liver over a period of:
- Weeks
- Years
- Decades
- Weeks- fatty liver (reversible)
- Years- alcoholic hepatitis
- Decades- cirrhohis
In simple terms explain how varices can form in the GI tract
due to protal hypertension
- fibrosiss of live means the liver cannot expand- therefore veisn that enter the liver will be compressed
- increased BP in portal system therefore blood shunts from portal system tp the systemic ciruclation via anastomes
escribe the effects of portal hypertension on kidney function in Hepatorenal syndrome
decreased renal function
activation of symapthetic nervous system results in renal vasoncstriction and therefore reduced renal blood flow, reduced GFR - renal failure , even acute tubular necrosis (ATN)
Explain why you get dark urine in Post-Hepatic jaundice
- conjugated bilirubin (dark brown) is water soluble therefore can go intot he blood stream to the kidney
- post-hepatic jaundice means there is a blockage into the GI system therefore less excreted in faeces and more goes into the blood and filtered by the kidneys
What can cause a raised ALP (Alkaline Phosphatase) level on a Liver function test?
damage to the lining of the biliary tree
- Explain to a friend (in stages) how chronic alcohol misuse can eventually result in the formation of abdominal ascites
- increased fat depsoiton in the liver
- overtime increase in inflmamaortry cell influx
- chronic inflammation
- cirrhosis
- decrease expandability of liver
- compressed protal vein
- increased portal hypertension
- less albumin produced
- ascites
Explain to your friend (yes the one trying to ignore you right now) how hepatocellular injury can lead to a mixed conjugated and unconjugated hyperbilirubinaemia
hepatocellular disease can cause a mixed unconjugated and conjugated hyperbilirubinemia due to both impaired bilirubin conjugation and canalicular excretion
drgrvtd in conjugated bilirubin excretion cause isolated conjuagted hyperbilirubinemia without cholestasis
cholestasis
Cholestasis is a liver disease. It occurs when the flow of bile from your liver is reduced or blocked. Bile is fluid produced by your liver that aids in the digestion of food, especially fats. When bile flow is altered, it can lead to a buildup of bilirubin.
(i) Name two of the three paired salivary glands (2x 1⁄2 marks)
