Ileal resection increases diarrhea risk primarily due to loss of what?

• A. Bile salts
• B. Vitamin B12
• C. Water
• D. Potassium

Answer: (A)

Loss of bile acids due to ileal resection disrupts enterohepatic circulation and increases bile acids reaching the colon. In the colon, these bile acids act as detergents and stimulate water and electrolyte secretion and accelerate transit, producing a watery diarrhea known as bile acid–induced diarrhea. This is the primary mechanism by which an ileal resection raises diarrhea risk.

Vitamin B12 absorption also occurs in the terminal ileum, but B12 deficiency tends to develop over time and is not the immediate cause of diarrhea. Water loss and potassium loss can accompany diarrhea, but they are consequences rather than the main driver in this scenario.