Bilirubin and jaundice

Question 1

what is bilirubin

Answer 1

this is a byproduct of the processing of haem from haemoglobin. which is removed from old blood cells

Question 2

describe the flow chart of haem and bilirubin

Answer 2

in the spleen the haem is converted to unconjugated-bilirubin. this unconjugated is then carried to the liver bound to albumin and then converted to conjugated bilirubin.
from the liver the conjugated bilirubin is excreted from the liver into the GI system.
in the GI system bacteria convert it into urobilinogen. some of this is then reabsorbed and re-excreted in urine.
but most urobilinogen is oxidised to stercobilin which is the pigment of faeces

Question 3

what can happen to bilirubin once its in the GI system

Answer 3

it will be converted to urobilinogen by bacteria in the GI tract.
this urobilinogen is either reabsorbed and then excreted renally.
most of it however will be oxidised to the stercobilin which gives poo its brown colour.

Question 4

what are urine bilirubin and urine urobilinogen measures of

Answer 4

urine bilirubin is a measure of the conjugated bilirubin in the blood.
urine urobilinogen is a measure of the conjugated bilirubin in the gut

Question 5

if excess bilirubin is filtered into urine what happens

Answer 5

the urine goes a deep orange brown colour.

Question 6

what is jaundice

Answer 6

clinical manifestation of hyperbilirubinaemia which is characterised by the yellowish pigmentation of the skin and sclera.

Question 7

why do we get pre-hepatic jaundice what are some causes

Answer 7

this is due to the accumulation of unconjugated bilirubin from things like haemolysis

Question 8

why do we get hepatic jaundice and what are some causes

Answer 8

this is due to the reduced ability of the liver to conjugate bilirubin.
acutely - acute hepatitis, acute fatty liver
chronic - chronic viral hepatitis, cirrhosis, gilberts syndrome

Question 9

why do we get post hepatic jaundice and whats the causes

Answer 9

this is mostly due to obstruction of the bilirubin excretion from the gall bladder.
intrahepatic causes - acute viral hepatisis causing swelling, cirrhosis causing obstruction, primary biliary cholangitis
extrahepatic cholestais - gall stones, pancreatic cancer, pancreatitis

Question 10

what are our amino transferases

Answer 10

ALT - alanine
AST - aspartate

Question 11

what do we see in haemolysis causing jaundice

Answer 11

this is the major prehepatic cause.
unconjugated hyperbilirubinaemia.
so haem is up, unconjugated is greatly up as too much unconjugated is being made for the liver to handle.
urine bilingoen up as there is increased bilirubin excretion.
total bilirubin is up as well. and there is moderate increase in AST. all else normal.

Question 12

what is gilberts syndrome, how does it cause jaundice and what results will we see from gilberts syndrome jaundice

Answer 12

genetic variant of the UGT1A1 gene which is normally responsible for bilirubin conjugation. hence we get increased unconjugated bilirubin . this presentation is intermittent with infection usually.

Question 13

what lab results will we see in acute hepatitis causing jaundice

Answer 13

unconjugated will be upslightly, conjugated is the main cause of the jaundice due to intrahepatic cholestasis from liver swelling. with increased Conjugated we thus get increased urine bilirubin.
total bilirubin up, urine bilirubin is up, AST and ALT up in a one to one ratio

Question 14

what lab results will we see in alcoholic liver disease causing jaundice

Answer 14

increase conjugated, with total bilirubin being increased. majorly raised GGT, raised AST:ALT, with the ratio being greater than 2.

Question 15

what lab results will we see in cirrhosis/ late alcoholic liver disease

Answer 15

increase in conjugated bilirubin but the degree of cholestasis can be variable in cirrhosis, with the increase in conjugated bilirubin proportional to the cholestatic degree, the key indicator of cirrhosis is low albumin. GGT may increase if its alcohol related. the AST, ALT and ALP increases are normal or mild due to the total liver damage from the process of cirrhosis

Question 16

what lab results will we see in primary biliary cholangitis

Answer 16

this is a cause of intrahepatic cholestasis. an autoimmune disease characterised by the destruction of the hepatic bile ducts.
increase in conjugated bilirubin due to the destruction of the bile ducts. hence as it cant be excreted the urine bilirubin also increases
as the obstruction becomes more profound the urobilinogen can decrease
total bilirubin up, urine bilirubin up, ALP up, GGt may be up a bit as well.

Question 17

primary biliary cholangitis what is it

Answer 17

this is a cause of intrahepatic cholestasis. an autoimmune disease characterised by the destruction of the hepatic bile ducts.

Question 18

what lab results do we expect to see from extraheptic cholestasis

Answer 18

this is caused by significant obstruction of the biliary system. can be from external blockage or internal blockage
depending on the degree of blockage Unconjugated may change.
conjugated and urine bilirubin are both up lots. as it cant be excreted to it goes to the urine.
hence urobilinogen and urine bilinogen go down due to the obstruction
total bilirubin and urine up. urine bilinogen is down. AST and ALT up mildly. ALP is up, GGT may be up

Question 19

what lab results will we see in gallstones

Answer 19

total and urine bilirubin up as it is a blockage. urine bilinogen low or absent. AST and ALT up. ALP up huge. mild moderate GGT up.