Which of the following best describes the consequence of extensive ileal loss?

• A. No significant consequence
• B. Significant malabsorption requiring lifelong B12 supplementation if the ileum is removed
• C. Only transient diarrhea
• D. Increased bile acid absorption

Answer: (B)

Extensive loss of the ileum disrupts two key absorptive pathways, with the most clinically important being vitamin B12 uptake. The terminal ileum is where the B12-intrinsic factor complex is absorbed, so removing or greatly impairing this segment leads to progressive B12 deficiency over years, causing megaloblastic anemia and neuropathy that requires lifelong supplementation (usually injections) to prevent symptoms. While bile acids are also poorly reabsorbed when the ileum is lost, contributing to diarrhea and fat malabsorption, the defining long-term consequence that drives the need for ongoing treatment is B12 deficiency. So the best description is significant malabsorption requiring lifelong B12 supplementation if the ileum is removed. The other options underestimate the impact or misstate the direction of bile acid handling.