The d-xylose absorption test is used to assess the absorptive ability of the intestine.

The d-xylose absorption test is used to assess the absorptive ability of the intestine.

• A. d-Xylose test
• B. Lactose tolerance test
• C. Fecal fat
• D. Serum albumin

Answer: (A)

The main concept is assessing the small intestine’s ability to absorb nutrients by using a compound that is taken up by the mucosa independently of digestive enzymes. D-xylose is absorbed in the proximal small intestine by passive diffusion and is not processed by the gut, so the amount that appears in the urine after a dose reflects the absorptive surface area of the mucosa itself. If urinary excretion is low, it points to mucosal damage or reduced absorptive capacity, as seen in conditions like celiac disease or enteritis. If the problem were pancreatic in origin, d-xylose absorption would typically be normal because pancreatic enzymes aren’t required for its uptake. In contrast, the lactose tolerance test evaluates lactase enzyme activity and carbohydrate digestion rather than overall mucosal absorption; fecal fat testing assesses fat malabsorption but doesn’t directly measure the mucosal surface’s ability to absorb sugars; serum albumin reflects nutritional status and protein levels rather than a direct test of intestinal absorptive function.

The main concept is assessing the small intestine’s ability to absorb nutrients by using a compound that is taken up by the mucosa independently of digestive enzymes. D-xylose is absorbed in the proximal small intestine by passive diffusion and is not processed by the gut, so the amount that appears in the urine after a dose reflects the absorptive surface area of the mucosa itself. If urinary excretion is low, it points to mucosal damage or reduced absorptive capacity, as seen in conditions like celiac disease or enteritis. If the problem were pancreatic in origin, d-xylose absorption would typically be normal because pancreatic enzymes aren’t required for its uptake.

In contrast, the lactose tolerance test evaluates lactase enzyme activity and carbohydrate digestion rather than overall mucosal absorption; fecal fat testing assesses fat malabsorption but doesn’t directly measure the mucosal surface’s ability to absorb sugars; serum albumin reflects nutritional status and protein levels rather than a direct test of intestinal absorptive function.