we studied the sites of production and absorption of b12 analogues by measuring serum vitamin b12 and analogues in 93 patients with various gastrointestinal diseases : pernicious anemia ( pa ) , ileal resections , ileitis , crohn 's colitis , ulcerative colitis , and irritable bowel syndrome ( ibs ) .
C0017178
gastrointestinal diseases
C0022104
irritable bowel