Here’s a little question to see if you remember the different causes of conjugated and unconjugated bilirubinemia
While examining the gums of a 25 year old patient, a yellowish discoloration of the oral mucosa and sclera is noted. Laboratory tests show a significant increase in unconjugated bilirubin. Which of the following disorders is most likely the cause of this patient’s abnormalities?
A. A stone in the bile duct
B. Carcinoma of the head of the pancreas
C. Pancreatic pseudocyst
D. Sickle cell disease
E. Hepatocellular carcinoma
Let’s review a little before we get to the question.
Bilirubin is a breakdown product of heme (which, in turn is part of the hemoglobin molecule that is in red blood cells). It is a yellow pigment that is responsible for the yellow color of bruises, and the yellowish discoloration of jaundice.
When old red cells pass through the spleen, macrophages eat them up and break down the heme into unconjugated bilirubin (which is not water soluble). The unconjugated bilirubin is then sent to the liver, which conjugates the bilirubin with glucuronic acid, making it soluble in water. Most of this conjugated bilirubin goes into the bile and out into the small intestine. (An interesting aside: some of the conjugated bilirubin remains in the large intestine and is metabolized into urobilinogen, then sterobilinogen, which gives the feces its brown color! Now you know.)
So: if you have an increase in serum bilirubin, it could be either because you’re making too much bilirubin (usually due to an increase in red cell breakdown) or because you are having a hard time properly removing bilirubin from the system (either your bile ducts are blocked, or there is a liver problem, like cirrhosis, hepatitis, or an inherited problem with bilirubin processing).
The lab reports the total bilirubin, and also the percent that is conjugated vs. unconjugated. If you have a lot of bilirubin around and it is mostly unconjugated, that means that it hasn’t been through the liver yet – so either you’ve got a situation where you’e got a ton of heme being broken down (and it’s exceeding the pace of liver conjugation), or there’s something wrong with the conjugating capacity of the liver (like a congenital disorder where you’re missing an enzyme necessary for conjugation – for example, Gilbert syndrome).
If you’ve got a lot of bilirubin around and it’s mostly conjugated, that means it’s been through the conjugation process in the liver – so there’s something preventing the secretion of bilirubin into the bile (like hepatitis, or biliary obstruction), and the bilirubin is backing up into the blood.
Back to our question. Let’s go through each answer and see what kind of hyperbilirubinemia these disorders would cause.
A. A stone in the bile duct. If big enough, a stone here could block the excretion of bilirubin into the bile. The bilirubin would already be conjugated, so this would be a conjugated bilirubinemia.
B. Carcinoma of the head of pancreas. This could also cause biliary obstruction, similar to A. (An important aside: it’s nice when pancreatic carcinomas announce themselves this way, because it may allow for earlier detection of the tumor. Unfortunately, this is uncommon. Pancreatic adenocarcinoma is usually silent until the tumor is very large and possibly metastatic.)
C. Pancreatic pseudocyst. Same idea as A and B.
D. Sickle cell disease. Sickle cell anemia is a type of hemolytic anemia. It could be a cause of unconjugated bilirubinemia, if the hemolysis is massive enough. If it’s just a low level of hemolysis, the liver could probably keep up, and you’d get a conjugated hyperbilirubinemia.
E. Hepatocellular carcinoma. This would fall into the category of blocking excretion of bilirubin. The bilirubin would already be conjugated – so this would be a conjugated hyperbilirubinemia.
So: since A, B, C and E produce only conjugated hyperbilirubinemia, the answer is D, sickle cell disease.
Awesome 10x helped alot
A very good question. Kristine’s explanation above helps to clarifying why D is the correct answer and not E which is what I thought of initially. Thanks.
Nice explanation.
Good explanation!!
Very Good one!!
This is Pathophysiology made simple.
wow awesome explanation, thanks !!!
well explained
I appreciate this explanaion.I though it was E
By now I agree
Dude, thank you so so much, I have an exam in 48 hrs xoxoxoxoxox
Yay! Glad it helped 🙂
Thankyou for this very clear explanation, it helped a lot!
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This is very helpful explanation. Thank you very much.
Helped alot thanx <3
Nice explanation
Thank u soo much. …
Well explained…..
Now cleared from the confusion of cb nd ucb.
very clear and simple explanation so helpful
amazing explanatn
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Very helpful explanation, makes sense! Thanks!!
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it’s awesome well explained and very helpfull.
THANKS
It is nice to have an answer to a question.
it is very helpful explanation
thanks alot
That is the best explanation I’ve ever recieved. Thanks!
So helpful in preparation for my nursing exam. Thank you 🙂
Perfectttttttt explanation!!!
Thanks a lot. Its explained in very simple terms…i got what i was looking for.
Thanks for this explanation!!!
Brilliant explanation. Cleared all my doubts about bilirubin metabolism. Thanks.
Precise and helpful. Thanks
This is so incredibly helpful, thanks a bunch! 🙂
Nice lovely explanation it quenched my thirst
thanks for making it simple
Well explained. . Awesome explanation. I thought dat why ans is D not E initially. .
Your explanation solved all my doubts at all the correct places. Thanks a ton! 🙂
I had a doubt though, what will happen in a parasitic infection affecting the liver like in Fasciola( in case of animals the flukes migrate in the liver). What type of hyperbilirubinemia will be seen then?
Hmm I’m not sure about that one – I would think it would be more of an obstructive pattern (conjugated hyperbilirubinemia) but have not seen that in real life!
It really helped
Thanks this is very helpfull…i like ur writing style
Very brief and understandable, thank U
very useful and nice explanation thank you so much…
Nice explanation….
wow great yar!!!..it actually cleared my whole thing about conjugated and unconjugated..thanq