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* bilirubin/ urobilinogen
 #530328  
  preets - 09/02/10 11:04
 
  hi all...
i am really confused about bilirubin especially about urine urobilinogen and urine bilirubin (urobilirubin)

i only understand unconjugatd bilirubin is inc in hemolytic anemia
and conjugated inc in liver problems

i don't have that concept clear...
if someone can pls help me with that
 
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* Re:bilirubin/ urobilinogen
#2184180
  adrianfadem - 09/02/10 11:10
 
  see if this link helps first...

http://www.usmleforum.com/files/forum/2010/1/503140.php

Cheers!
Adrian
 
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* Re:bilirubin/ urobilinogen
#2184193
  ariadnac06 - 09/02/10 11:14
 
  Hi Mr Cheers :) where you have been Adrian…good to see you back…

Cheers :))
 
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* Re:bilirubin/ urobilinogen
#2184210
  adrianfadem - 09/02/10 11:26
 
  thats Ms Cheers! to you! LOL!

its all good....! yeah its been awhile huh?... very good to see u still here too!! : )

(i love mini reunions.. especially at the expense of other people's threads.... cruel me..)

Cheers!
Adrian
 
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* Re:bilirubin/ urobilinogen
#2184211
  ariadnac06 - 09/02/10 11:26
 
  preets I had the same questions a while ago and somebody very sweet from his forum took the time to explain to me, so I will post the same explanation this kind person did to me…take the time write it down and you will understand perfectly....

Ok im going to write all in my simple words so will try to make it easy
1st simple term understanding
1]unconjugated bilirubin ---water insoluble [cant come in urine]
2]conjugated bilirubin -----water soluble [can be excreted in urine and wen it comes in urine its called ‘’urine bilirubin’’ ;get this point ;it is only confusing u..]
3]Urobillinogen---when conjugated bilirubin comes in intestine …its get degraded by intestinal bacteria to form urobillinogen

---let me 1st explain how bilirubin metabolism is---
Whenever there is breakdown of rbcs unconjugated bilirubin is formed [this is lipid soluble ie water insoluble] ;this unconju bilirubin binds with albumin and then transported to liver .
In liver we have enzyme UGT which converts unconjugated billirubin to conjugated billirubin which is water soluble .Now this water soluble conjugated bilirubin is secreted in to bile ducts [this process is active process which needs ATP (99er point).]
Now this conjugated billirubin through bile duct comes in to duodenum where it will be converted to
Urobillinogen .
Urobillinogen---when conjugated bilirubin comes in intestine …its get degraded by intestinal bacteria to form urobillinogen .Now suppose 100 % urobillinogen is formed ; which further get converted to urobillin. Now 80% of urobillin it get in to stool .
We are now left with 20 % urobillin 90% [90% of 20%] of this goes back to liver through portal circulation [ur secret pathway] and this is called enterohepatic circulation .
and remaining 10% urobillin excreted in to gives coloure to urine

now ur doubt
1] In extra vascular hemolysis. The RR book said that the Urine conjugate bilirubin is absent??? How come it is absent if there are more hemolysis , therefore more unconjugated bilirubina reaching the liver to be conjugated, therefore there aere mor conjugated bili passing to small intestine and kidney, that’s why Uriine urobilinogen (UBG) is high, but Why not Urine bilirubin??
Ans—in hemolysis we are producing excess amount of unconjugated billirubin which is big load to liver
liver conjugates maximum amount of unconjugated bilirubin and send it to intestine through bile duct .remenber here bile ducts have no pathology neither liver has any pathology so conjugated bile will nicely pass to intestine .[conjugated billirubin will not spill through the ducts so no conjugated billirubin comes in to urine [again im insisting here—when conjugated bilirubin comes in to urine its called urine billirubin]
now becoz more than normal amount of conjugated bilirubin is cming to intestine more urobillinogen is formed so urine urobillin is excreted [ according to Goljan in his audios urobillinogen and urobillin are same term ;no much difference .they are one and the same]
In summery in extravacular hemolysis
Uncojugated billirubin ---very high
Conjugated billirubin---less than 20% [20% just a term comparing to amt of uncojugated billirubin]
Urine billirubin ---ABSENT
Urine billirubinogen –increased
Liver enzymes ---NORMAL
Now 2nd
2.- Viral hepatitis. Why conjugated bilirubin in urine is high??? In liver damage there is no problem with unconjugated bili, but when reach liver I believe some is congujated and some don’t. The one that is not conjugated is shift from the liver to the kidney (I didn’t know that) sounds like secret passageway  that’s why Urine bilinogen is high. But If there is no too much conjugation why the bilirubin in urine is high???
Ans –in hepatitis we have damage to liver canaliculi and bile ducts .watever unconjugated bilirubin cming is in normal limit and depending upon liver damage ..liver will try to convert unconju billirubin to conjugated bilirubin [say about 20 -50%] but here as canaliculi and bile ducts are damaged ..water soluble conjugated bilirubin spills out mixed in to blood and excreted in to the urine ;thus urine bilirubin is high and also some conjugated bilirubin is also going in to intestine where it will be again converted to urobilinogen and part of it goes into enterohepatic circulation and part of it to urine as urobilinogen
In summer—
In liver damage or hepatitis we will get mixed jaundice
1]unconjugated billirubin—almost normal
2]conjugated billirubin -20—50% [amt compared to unconjugated bilirubin]
3]urine billirubin –present
4]Urine bilirubinogen –present
5]Liver enzymes---very high s/o liver injury
Now last one
In obstructive liver disease. Why Urine urobilinogen is high??? I believe that the conjugated bilirubin is converting by bacterias in the intestine to urobilinogen, but there is an obstruction how this conjugated bili reaches the bowel???

Ans--–[here u are saying urine urobilinogn is high???—check it pasted here—im sorry ur totally wrong urine urobillinogen is totally absent in obstru jaundice]

Obstructive jaundice means there is obstruction to bile flow from liver to intestine through bile duct .
Remember uncojugated bilirubin is normal [ie no extra hemolysis] ;liver is normal [so all uncojugated billirubin is getting conjugated properly] but transfer of billirubin to intestine through duct is not occurring due to obstruction say due to bile duct stone
So wats happening? No conjugated billirubin is cmonig to intestine so no urobillinogen is formed so no coloure to stool [pale coloure to stool ] same time no urobillinogen in urine and no enterohepatic circulaton .
But but urine billirubin is high …why??? Becoz as bile is nt flowing and getting accumulated in to bile ducts or ductules …due to back pressure ducts will rupture and conjugated billirubin spills in to urine and urine billirubin is high..
In summery
1]unconjugated bilirubin –near normal
2]conjugated billirubin –above 50%
3]urine billirubin –highh
4]urine urobilinogen –absent
5]liver enzymes –NORMAL
6]alkaline phosphatase –HIGH



 
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* Re:bilirubin/ urobilinogen
#2184506
  betssy1470 - 09/02/10 14:43
 
  very nice ezplanation ariadna, thanks...........  
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* Re:bilirubin/ urobilinogen
#2184523
  rawalian - 09/02/10 14:57
 
  hey thanx a lot .... helped a lot... BIG TIME....  
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* Re:bilirubin/ urobilinogen
#2187315
  elpida - 09/05/10 07:58
 
  Hello Ariadnac,

Thank you so much for the nice explanation. There is a point I do not understand:
"The one that is not conjugated is shift from the liver to the kidney (I didn’t know that) sounds like secret passageway  that’s why Urine bilinogen is high."

Could you please explain that further if you can?

Thanks a lot,

Elpida
 
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