Vitamin B12 is principally absorbed in the terminal ileum, an intestinal segment that the case patient no longer has. The vitamin B12 intrinsic factor unit complexes with bile acids and is absorbed via proteins that are present in ileal mucosal cells. Thus, the patient cannot absorb vitamin B12. Patients with vitamin B12 deficiency can present with ataxias (which can lead to falls), confusion, paresthesias in the extremities, and occasionally diarrhea.
