Why are resections of the proximal bowel generally better tolerated?

• A. Ileal compensation and adaptation
• B. Jejunal compensation and adaptation
• C. Colon compensation and adaptation
• D. Stomach compensation and adaptation

Answer: (A)

When part of the proximal small intestine is removed, the remaining ileum becomes the main site for absorption and has a remarkable ability to adapt. The ileum can undergo mucosal hyperplasia, with taller villi and deeper crypts, and it upregulates transporters for nutrients and bile acids. These adaptive changes expand the effective absorptive surface and improve nutrient and fluid uptake, allowing the gut to compensate for the lost proximal segment. The colon can help with water absorption to some extent, but it doesn’t replace small-bowel nutrient absorption. Removing distal segments like the ileum would remove the key site for bile-acid reabsorption and vitamin B12 uptake, causing more severe malabsorption, which is why proximal resections are generally better tolerated.