Bilirubin Practical Flashcards
What is the normal range for bilirubin
2-20 umol/L
What causes the faeces to be brown
Normally bilirubin is conjugated in the liver to give bilirubin diglucuronide and then secreted in the intestine. Bacteria in the gut oxidise to uncoloured urobilinogens (sterobilinogen) which are then oxidised to urobilins (stercobilin) which are coloured and cause faeces to be brown
What are the two possible causes of pale stools
Bilirubin metabolism is abnormal or the ducts leading from the liver to the duodenum are blocked so that although conjugated bilirubin is formed it cannot be excreted
What makes stools pale
No urobilinogens are formed as no conjugated bilirubin is excreted. There is an absence of urobilins (stercobilin) causing the stool to be pale
What is the cause of dark urine
Liver is still functioning so that conjugated bilirubin is produced but the ducts are blocked
What makes urine dark
The ducts are blocked resulting in conjugated bilirubin leaking from the hepatocytes and entering the blood stream. There are increased amounts of conjugated bilirubin in the blood leading to increased excretion of the bilirubin pigment in the urine which gives the urine a dark orange colour
Why is skin discoloured (yellow)
Due to a buildup of bilirubin in the skin. Bilirubin has a high affinity for the elastic fibers in the skin’s connective tissue, it binds to the fibers resulting in the yellow colouration
Why is the sclera affected early with discolouration
The sclera has a high content of elastin which has a high affinity for bilirubin
Why is skin itchy
Due to bile salts.
What causes itchiness
2/3 of organic material in bile is bile salts formed by the conjugation of bile acids with taurine or glycine. As teh hepatocytes swell some may apoptose. Due to the back flow from the obstructed bile ducts, bile salts will enter the blood stream
What is a normal Gamma GT value
5-45 IU/L
What does a high Gamma GT value indicate
There is a problem with the hepatocytes or bile ducts, which is where this enzyme is normally situated
What does both a raised GGT and ALP indicate
Liver or bile ducts damage, the fact that both are high suggests cholestatic jaundice
What would only high ALP suggest
The ALP was of bone or placental origin
What would only high GGT suggest
The hepatocellular damage was drug-induced e.g. alcohol
What does a normal AST result indicate
The problem is not related to the liver cells (hepatocytes)
What does a high GGT, high ALP and normal AST say about this type of jaundice
The results indicate cholestatic jaundice which is a pathological condition of impaired bile formation and bile flow. It can be caused by extrahepatic or intrahepatic obstruction or by defects in hepatocyte secretion.
What is the suggested caused of abdominal pain with high GGT, high ALP and normal AST
Due to a biliary obstruction by the tumour so post-hepatic cholestatic jaundice
What would be the expected liver function test results in cholestatic jaundice
High GGT, high ALP and normal AST