Pathoma Wrong?

[qw098]

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For extravascular hemolysis.. it says urine will be dark due to increased urine urobilinogen... if there is increased urine urobilinogen.. urine won't be dark.. on the contrary it will be more clear/yellow.. no?

Dark urine is caused by increase of conjugated bilirubin when there is biliary tract obstruction - no? And thus a decrease in urine urobilinogen..?

 

[seminoma]

Doesn't urobilinogen --> urobilin --> pigment?

 

[BlueJay25]

Bilirubin --> urobilinogen
Urobilinogen in the urine gets converted to urobilin when the urine is oxidized (so when it hits the air) and the urobilin is the yellow pigment you see in urine.
Urobilinogen in the GIT either gets converted to stercobilin directly or into stercobilinogen which will then be converted to stercobilin when the feces are oxidized (so when it hits the air) and the stercobilin is the brown pigment you see in feces.

It was cool for me to learn because if the feces/urine were never oxidized they would not be the colors we know them as:
if you were to micturate in space, your urine would clear because the urobilinogen wouldn't be oxidized into urobilin
if you were to defecate in space, your stools would be a grayish color because most the urobilinogen --> stercobilinogen wouldn't be oxidized into stercobilin except the small amount of urobilinogen that gets directly converted to stercobilin.

That's my best understanding of the topic.

 

[scoKraz4]

Urobilinogen/urobillin are yellow. Normally urobilinogen gets absorbed in the GI tract and then is oxidized into urobilin in the blood and pee'd out. If you are dealing with higher concentrations of this stuff like in hemolysis, more urobilinogen will probably spill into the urine than normal and miss out on being oxidized. Regardless, both are a yellowy pigment and increased concentrations of them will make the urine a darker yellow. So "dark urine" as mentioned in the table.

 

[Robotic Dock]

Urobilinogen >>> Urobilin

 

[medmedman]

For extravascular hemolysis.. it says urine will be dark due to increased urine urobilinogen... if there is increased urine urobilinogen.. urine won't be dark.. on the contrary it will be more clear/yellow.. no?

Dark urine is caused by increase of conjugated bilirubin when there is biliary tract obstruction - no? And thus a decrease in urine urobilinogen..?

Listen to what Pathoma said. Yes, you increase UCB but it just hangs around the blood. EVENTUALLY it all goes to the liver to become CB. Now you have substantially increased CB (because you have the normal amount of CB coming in and this extra CB as a result of UCB that was just swimming around). This EXCESS CB will be broken down in the intestine, causing an EXCESS of urobilinogen.

 

[aspiringmd1015]

indirect bilirubin increases(jaundice), gets conjugated by the liver, becomes cb, some gets reabsorbed to be urinated out, as urobilinogen, and the more urobilinogen, the more urobilin, the more pigment. he states it very clear.

 

[aspiringmd1015]

****load of urobilin(yellow pigment)=****load of darkness