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Old 05-24-2012
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Liver Two Questions about the Pathophysiology of Jaundice?

1- can anyone explain to me why increase cholesterol in biliary disease , (psc) and others????

2- why in heamolytic jaundice, we have abscent urine bilirubin (acholuria)?? according to FA ???
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Old 05-24-2012
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1) Bile acids are made from cholesterol, and their excretion via the GIT is one way of getting rid of endogenous cholesterol. Even though 90% is reabsorbed in the ileum, the 10% excreted is important. In the case of biliary disease/cirrhosis the bile acid can't leave through the bile ducts (which are obstructed) and as a result their levels increase in the liver and blood. when bile acid levels go up in the liver, they inhibit those enzymes that convert cholesterol into bile acids, and this results in increased VLDL etc. One way to remember this is; the use of bile sequestrant drugs to lower cholesterol. If these drugs bind to bile and inhibit their reabsorption in the ileum, then more bile is excreted. Since less bile is reaching the liver via the enterohepatic circulation, the liver ends up making more bile acids from cholesterol. So you're essentially excreting endogenous cholesterol.

2) In hemolytic jaundice, the problem is too much break down of RBC's. So unconjugated bilirubin goes up, but this is not water soluble and is bound to albumin. so you won't find it in the urine. once the increased UCB reaches the liver, it gets conjugated and secreted as bile. Since the liver is fine and you have no posthepatic obstruction, the conjugated bilirubin will reach the intestines and get converted to urobilinogen. I think around 90% of the urobilinogen is excreted as stercobilin and 10% is reabsorbed (colon). Since you have a lot more UCB due to the hemolysis, this will increase the amount of CB reaching the intestines and therefore more urobilinogen will be produced. This means there's going to be more urobilinogen reabsorbed, and more of it will also get to the urine.
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Old 05-24-2012
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thanks alot , for 1
but for 2 , that is what I think as well but FA says it decrease that is what made me confused
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For 2, bilirubin should be absent in urine, but urobilinogen will be increased. So FA is right.
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Quote:
Originally Posted by slowpoke View Post
For 2, bilirubin should be absent in urine, but urobilinogen will be increased. So FA is right.


that is my question why it should be decrease in urine ???
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Quote:
In hemolytic jaundice, the problem is too much break down of RBC's. So unconjugated bilirubin goes up, but this is not water soluble and is bound to albumin. so you won't find it in the urine.
The excess UCB is conjugated in the liver and secreted through the bile ducts, the conjugated bilirubin is converted to urobilinogen in the intestines. You won't have CB showing up in the blood cuz the liver/bile apparatus are all working fine.

You'll only see increased conjugated bilirubin in the urine if there was a problem with the liver or bile ducts.
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