A qbank question talks about a guy who undergoes total gastrectomy after an invasive gastric cancer and asks which supplement does he require for the rest of his life.
Answer choice came down to gastric enzyme and water soluble vitamin.
The correct answer was water soluble vitamin. I don't understand why this would be, I would think that supplementing intrinsic factor would be the more correct answer.
Without intrinsic factor, B12 can't be absorbed, right?
I remember this question on Uworld and the explanations contradicted themselves with other Uworld questions. The best answer is still B12 parenteral for life. But its not the only one as the question would lead you to believe. You may have to supplement folate fat soluble vitamins and/or calcium for life as well, or at least for a while.
When a gastrectomy is done there are a few different approaches that depend on why they are doing it in the first place. You can have the entire stomach removed, or you can have the antrum removed and sew the remaining stomach to the continuing section of the duodenum, or you can take out the antrum and sew the remainder of the stomach to the jejunum or ileum, but you would still keep the duodenum connected to the bile duct in order to keep bile salts and pancreatric enzymes flowing in. I'm sure there's more options but those are the ones I know of, gastrectomy can mean 50 different things.
Usually any of the options will have the dumping syndrome as a consequence of the surgery, but depending on which option was performed the dumping syndrome may subside. So the patient will probably have malabsoption of B12, folate, fat soluble vitamins, and Calcium. The anemias from B12, folate, or iron deficiency present late, its not an immediate consequence. It's possible that the GI system will adapt and begin to produce IF in the duodenum or jejunem. So in theory you may or may not need to supplement B12. Actual protocol depends on this, whether or not the patient is able to make his own IF and whether or not he is compliant with oral supplementation. B12 binding to IF also depends on whether or not the pH is acidic in the duodenum, which would depend on the type of gastrectomy, but it would be a better bet to assume it won't be as alkaline as it should be therefore even if there is IF it would have trouble binding B12.
Anyways the best answer for the question is B12. For starters because Intrinsic factor is not an enzyme, its a protein that transports B12. Not all proteins are enzymes, if its not catalyzing any reaction (which IF is not) then its not an enzyme. Therefore B12 is the better answer. And of note, I did see that question on some NBME and the answer was B12 for life (but it may have been an older NBME, and protocols may have changed since then or the condition may have been gastrectomy due to pernicious anemia, don't remember).
