Question:
A 41 year old patient presented with chronic diarrhea for 3 months. A d-xylose absorption test was ordered to look for:
A 41 year old patient presented with chronic diarrhea for 3 months. A d-xylose absorption test was ordered to look for:
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D-xylose needs only an intact gut mucosa, not pancreatic enzymes, to be absorbed.
Updated On: Jul 8, 2026
- Carbohydrate malabsorption due to mucosal disease.
- Carbohydrate malabsorption due to chronic pancreatitis.
- Fat malabsorption due to mucosal disease.
- Fat malabsorption due to chronic pancreatitis.
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Verified By Collegedunia
The Correct Option is A
Solution and Explanation
Step 1: Understanding the Question:
A patient has chronic diarrhea and needs a test that tells whether the small bowel lining (mucosa) is intact or whether the problem lies outside the gut, such as in the pancreas.
Step 2: Key Concept:
D-xylose is a simple sugar. It does not need pancreatic enzymes or bile salts to be absorbed, it only needs a healthy small intestinal mucosa to cross into the blood. After an oral dose, the amount that appears in blood or urine tells us if the mucosa can absorb a simple sugar.
Step 3: Detailed Explanation:
If the mucosa is damaged, as in celiac disease, tropical sprue or Whipple's disease, D-xylose is not absorbed properly and blood/urine levels stay low. This is an abnormal (low) D-xylose test.
If the problem is chronic pancreatitis instead, the mucosa is normal, only the pancreatic enzymes that digest fat and complex carbohydrates are missing. Since D-xylose does not need these enzymes, the test stays normal in pure pancreatic disease.
So a low D-xylose test points to mucosal disease causing malabsorption of a simple sugar (carbohydrate), not to pancreatic disease and not to fat malabsorption, since xylose is a sugar, not a fat.
Step 4: Why the other options are wrong:
Option 2 is wrong because chronic pancreatitis gives a normal D-xylose test, the defect there is enzyme lack, not mucosal damage.
Option 3 is wrong because D-xylose tests sugar absorption, not fat absorption.
Option 4 is wrong for the same reason, plus pancreatitis does not lower D-xylose levels.
Step 5: Final Answer:
The D-xylose test is used to detect carbohydrate malabsorption caused by small bowel mucosal disease.
\[ \boxed{\text{Carbohydrate malabsorption due to mucosal disease}} \]
A patient has chronic diarrhea and needs a test that tells whether the small bowel lining (mucosa) is intact or whether the problem lies outside the gut, such as in the pancreas.
Step 2: Key Concept:
D-xylose is a simple sugar. It does not need pancreatic enzymes or bile salts to be absorbed, it only needs a healthy small intestinal mucosa to cross into the blood. After an oral dose, the amount that appears in blood or urine tells us if the mucosa can absorb a simple sugar.
Step 3: Detailed Explanation:
If the mucosa is damaged, as in celiac disease, tropical sprue or Whipple's disease, D-xylose is not absorbed properly and blood/urine levels stay low. This is an abnormal (low) D-xylose test.
If the problem is chronic pancreatitis instead, the mucosa is normal, only the pancreatic enzymes that digest fat and complex carbohydrates are missing. Since D-xylose does not need these enzymes, the test stays normal in pure pancreatic disease.
So a low D-xylose test points to mucosal disease causing malabsorption of a simple sugar (carbohydrate), not to pancreatic disease and not to fat malabsorption, since xylose is a sugar, not a fat.
Step 4: Why the other options are wrong:
Option 2 is wrong because chronic pancreatitis gives a normal D-xylose test, the defect there is enzyme lack, not mucosal damage.
Option 3 is wrong because D-xylose tests sugar absorption, not fat absorption.
Option 4 is wrong for the same reason, plus pancreatitis does not lower D-xylose levels.
Step 5: Final Answer:
The D-xylose test is used to detect carbohydrate malabsorption caused by small bowel mucosal disease.
\[ \boxed{\text{Carbohydrate malabsorption due to mucosal disease}} \]
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