A 48-year-old woman had 80 cm of terminal ileum resected for Crohn's disease. Six months later she has chronic watery diarrhoea and steatorrhoea. Which mechanism best explains her diarrhoea?

• A Bacterial overgrowth deconjugating bile salts within a blind loop
• B Unabsorbed bile salts entering the colon and stimulating secretory diarrhoea ✓
• C Pancreatic exocrine insufficiency from loss of enterohormonal signalling
• D Osmotic diarrhoea from isolated glucose galactose malabsorption

Explanation

The terminal ileum is the specific site of active bile salt reabsorption through the apical sodium dependent bile acid transporter. Resection allows conjugated bile salts to escape into the colon, where they inhibit water absorption and stimulate secretion, causing watery diarrhoea, while depletion of the bile acid pool impairs micellar fat solubilisation causing steatorrhoea. Blind loop overgrowth needs retained stagnant bowel, and congenital sugar transporter defects present in infancy, not after surgery.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.