This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Stool osmotic gap is calculated by using the formula: 
Select and explain. 
A. 2 x (stool + stool ), B. 2 x (stool + stool ), C. 2 x (stool + stool ), D. 2 x (stool + stool )
A: 2 x (stool + stool )
Answer: A: 2 x (stool + stool ) 
Explanation: Stool osmotic gap is calculated by using the formula : 2 x (stool + stool ) stool osmolality When it is >50, an osmotic gap is present, suggests diarrhea is due to a non absorbed dietary nutrient, e.g., a fatty acid and/or carbohydrate. When this difference is <25, a dietary nutrient is not responsible for the diarrhea. Ref: Harrison, E-18, P-2460.