In a healthy adult on a typical Western diet, approximately how much fluid does the colon receive daily, and what is its maximum absorptive reserve?
- A Receives about 1 to 2 L/day and can absorb up to about 5 L/day before diarrhoea ensues ✓
- B Receives about 9 L/day and can absorb up to 9 L/day
- C Receives about 3 L/day and can absorb only 500 mL/day
- D Receives about 7 L/day and can absorb up to 7 L/day
Correct answer: A. Receives about 1 to 2 L/day and can absorb up to about 5 L/day before diarrhoea ensues
Explanation
The small intestine absorbs roughly 6 to 8 of the 9 L presented to it daily, delivering 1 to 2 L to the caecum. The healthy colon can absorb up to about 5 L/day, giving a large reserve. Diarrhoea appears only when ileal delivery exceeds this capacity or when colonic absorption itself is impaired.
Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.
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