A 41 year old patient presented with chronic diarrhea for 3 months. A D-xylose absorption test was order to look for:

D-Xylose - monosaccharide, or simple sugar, that does not require enzymes for digestion prior to absorption. Its absorption requires an intact mucosa only. In normal individuals, a 25 g oral dose of D-xylose will be absorbed and excreted in the urine at approximately 4.5 g in 5 hours. A decreased urinary excretion of D-xylose is seen in small intestinal bacterial overgrowth and Whipple's disease. In cases of bacterial overgrowth, the values of D-Xylose absorption return to normal after treatment with antibiotics. In contrast, if the D-xylose urinary excretion is normal, then the problem must be due to a non-mucosal cause of malabsorption (i.e., pancreatic insufficiency).