GI System MCAT Practice Question
A 42-year-old man with a 10-year history of Crohn's disease presents with progressive fatigue and diarrhea. He underwent resection of 50 cm of terminal ileum 6 months ago for refractory disease with strictures. Laboratory studies show hemoglobin 9.2 g/dL with macrocytic indices (MCV 110 fL), and 72-hour fecal fat is 8 g/day (normal <7 g/day). Despite oral iron supplementation and dietary modifications, his macrocytic anemia has worsened and he continues to have fatty stools. Which of the following best explains the mechanism underlying both his macrocytic anemia and steatorrhea following terminal ileal resection?
Answer choices
- ALoss of the ileocecal valve increases colonic transit time, reducing water and nutrient absorption
- BRemoval of specialized ileal epithelium eliminates the transporters required for vitamin B12 and bile acid reabsorptionCorrect answer
- CDecreased enterohepatic circulation of bile acids stimulates hepatic cholecystokinin secretion, inhibiting pancreatic lipase
- DSurgical stress causes permanent reduction in intrinsic factor production by gastric parietal cells
- EShortened intestinal length accelerates chyme transit, reducing absorption time for all nutrients equally
- FPost-resection inflammation triggers autoimmune destruction of intestinal brush border alkaline phosphatase
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