Which finding is di¬agnostic for malabsorptive syndrome?
A. Prominent villi on small intestine biopsyB. 3 g of D-xylose in a 5-hour urine collection
C. High carotene level with normal vitamin A intake
D. 4 g of fat on a 72-hour fecal fat collection
Ans. (B) 3 g of D-xylose in a 5-hour urine
collection
After a 25-g oral dose of xylose, a 5-hour
urine collection should contain at least 5 g of D-xylose. The finding of less
than 4-5 g of D-xylose in the stool is indicative of malabsorption syndrome.
Flat villi with inflammatory cell infiltration on small bowel biopsy are
characterized by celiac disease. The serum carotene level is a reflection of
vitamin A metabolism. Because vitamin A is a fat-soluble vitamin, a low serum
carotene level with normal vitamin A intake may be useful in screening for fat
malabsorption. A positive Sudan stain is indicative of an underlying
malabsorptive process. However, the gold standard test for fat malabsorption
is a 72-hour stool collection for fecal fat. The coefficient of fat absorption
in the small intestine is 7%. As a result, a patient consuming a 100-g fat diet
should have no more than 7 g of fat in the stool each day; more than 7 g of fat
would be consistent with a malabsorption syndrome.
