Absorptive function of the mucosa of intestine can be best assessed by –
**Core Concept**
The absorptive function of the intestinal mucosa is a critical process that involves the uptake of nutrients from the luminal contents into the bloodstream. This process is mediated by specialized transport mechanisms, including carrier proteins and enzymes, which facilitate the absorption of carbohydrates, proteins, and fats.
**Why the Correct Answer is Right**
The correct answer is **D. D-xylose test**. This test is a widely used method to assess the absorptive function of the intestinal mucosa. D-xylose is a monosaccharide that is absorbed by the small intestine through a specific transport mechanism. In healthy individuals, D-xylose is rapidly absorbed and appears in the bloodstream within 1-2 hours. In patients with intestinal malabsorption, the absorption of D-xylose is impaired, and its levels in the blood are decreased.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the Schilling test is used to assess vitamin B12 absorption, not the absorptive function of the intestinal mucosa as a whole.
**Option B:** This option is incorrect because the lactose tolerance test is used to assess lactose intolerance, which is a specific type of malabsorption, rather than the overall absorptive function of the intestinal mucosa.
**Option C:** This option is incorrect because the breath hydrogen test is used to assess carbohydrate malabsorption, particularly in patients with small intestine bacterial overgrowth (SIBO).
**Clinical Pearl / High-Yield Fact**
The D-xylose test is a useful tool for assessing intestinal malabsorption, particularly in patients with symptoms such as diarrhea, weight loss, and fatigue.
**Correct Answer:** D. D-xylose test