A 60-year-old man underwent extensive resection of the terminal ileum for Crohn's disease 10 years ago. He now presents with microcytic anaemia unresponsive to oral iron and has recently been found to have multiple gallstones. Which mechanism links both complications?

• A Bacterial overgrowth consuming dietary vitamin K
• B Chronic occult blood loss from residual inflamed mucosa
• C Impaired pancreatic enzyme secretion reducing iron solubilisation
• D Loss of the enterohepatic circulation of bile salts leading to bile acid depletion ✓

Explanation

The terminal ileum is the exclusive site of bile salt reabsorption and vitamin B12 absorption. Its loss interrupts the enterohepatic circulation, depleting the bile salt pool so cholesterol supersaturated bile forms gallstones, while malabsorbed bile acids entering the colon cause diarrhoea. Iron is absorbed in the duodenum and proximal jejunum, so iron deficiency here reflects chronic loss rather than malabsorption; pancreatic secretion and vitamin K pathways do not account for gallstones.

Reference: Ganong's Review of Medical Physiology, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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