Xylose absorption and its clinical significance.

1. Xylose absorption by the small intestine probably includes an active process. 2. For xylose testing, the 25-g dose appears to be preferable to 5 g. 3. Factors that influence the test result include intestinal bacterial overgrowth, reduced xylose metabolism in cases of liver disease, sequestration into ascites, age, and the state of renal function. 4. The test results differentiate patients with extensive disease of the upper small intestine from normal subjects, and from patients with steatorrhoea due to pancreatic insufficiency, in most but not all instances. Blood xylose levels combined with urinary xylose output aids discrimination.