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Old 02-27-2012
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Help I don't understand the Schilling test

regarding schilling test...just want to know why Vit b12 even after i.m injection and by oral route(the radioactive one) decreases in urine in pernicious anemia or malabsorbtion syndrome...i mean if there is no IF then neither B12 labelled or unlabelled will not be absorbed and its volume should actually increase in urine(not absorbed in gut and so increased in urine)please anyone explain this?? plz:sorry:..just don't understand it..
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doesn't this test involve two types of b12 administration? one being oral and one being IV/IM? and so the orally administered b12 will be pee'ed out, hence u have a GI problem.
or am i thinking of something else?
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yes..thats the test..okay i get that oral will be peed out..but when there's defiency of IF or malabsorbtion both oral and radioactive shud be peed out so we must get more of b12 in urine..but it says less of b12...reeally confused
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Old 02-27-2012
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B12 in mouth forms R complex, goes to stomach.
Stomach produces IF which goes together with R-complex to duodenum.
In duodenum, R-complex is destroyed and free B12 is bound to IF.
The complex is absorbed in the ileum.

Shilling test - oral (radioactive) supplement is followed by IM administration.
Radioactive b12 in urine suggests that it was absorbed (no pernicious anemia, all ok with the gut and so on)

If there is no radioactive b12 in urine - than the oral admission of radioactive vitamin comes with admission of intrinsic factor together (followed by IM admission)

IM administration is supposed to saturate liver receptors, but not enough to complietely replenish the body needs

The last one helps to diagnose the presence of possible autoantibodies against intrinsic factor (pernicious anemia)
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Explained here
Schilling Test for the USMLE exam

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Old 02-27-2012
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"So how they do the Schilling test?
Step 1: We have to saturate the B12 receptors with an Intramuscular injection of cyanocobalamine (vit. B12) because otherwise the body would be hungry for the oral dose of B12 and it won't appear in urine even if there was not pernicious anemia.
Step 2: Give a radiolabled oral B12 dose-> now if B12 appeared in the urine then the absorptive mechanisms must be working and the case is due to dietary deficiency. -> if it did not appear in the urine then we have now a case of B12 malabsorption but we don't know yet it's pernicious anemia or not therefore we proceed to step 3.
Step 3: We give an intrinsic factor and re-give the oral radiolabled B12. -> if the B12 appeared in the urine then the diagnosis is pernicious anemia. -> if the B12 still did not show up in the urine then it's malabsorption but not due to pernicious anemia and most commonly due to ileal resection or small bowel infection and bacterial over growth or fish tapeworm infestation.
Step 4: Giving tetracycline is sometimes done after this. If it corrects the abnormality then bacterial growth is suspected. Similarly giving pancreatic enzyme extracts with the oral B12 should guide towards pancreatic insufficiency if it corrects the abnormality."

copied from here
Schilling Test for the USMLE exam

makes sense.
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Quote:
Originally Posted by Sabio View Post
Thank u so much sabio..its an honour that u saw my post and replied to it..thanks a ton
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Quote:
Originally Posted by Dr.NickRiviera View Post
"So how they do the Schilling test?
Step 1: We have to saturate the B12 receptors with an Intramuscular injection of cyanocobalamine (vit. B12) because otherwise the body would be hungry for the oral dose of B12 and it won't appear in urine even if there was not pernicious anemia.
Step 2: Give a radiolabled oral B12 dose-> now if B12 appeared in the urine then the absorptive mechanisms must be working and the case is due to dietary deficiency. -> if it did not appear in the urine then we have now a case of B12 malabsorption but we don't know yet it's pernicious anemia or not therefore we proceed to step 3.
Step 3: We give an intrinsic factor and re-give the oral radiolabled B12. -> if the B12 appeared in the urine then the diagnosis is pernicious anemia. -> if the B12 still did not show up in the urine then it's malabsorption but not due to pernicious anemia and most commonly due to ileal resection or small bowel infection and bacterial over growth or fish tapeworm infestation.
Step 4: Giving tetracycline is sometimes done after this. If it corrects the abnormality then bacterial growth is suspected. Similarly giving pancreatic enzyme extracts with the oral B12 should guide towards pancreatic insufficiency if it corrects the abnormality."

copied from here
Schilling Test for the USMLE exam

makes sense.
finally got it..writing it to my notes in FA..great explanation..
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