What is involved in D-xylose test in the workup of exocrine pancreatic insufficiency (EPI)?

Updated: Aug 12, 2021
  • Author: Samer Al-Kaade, MD; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
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If the 72-hour fecal fat collection results demonstrate fat malabsorption, the D-xylose test is used to document the integrity of the intestinal mucosa.

D-xylose is readily absorbed in the small intestine. Approximately half of the absorbed D-xylose is excreted in urine without being metabolized. If absorption of D-xylose is impaired by either a luminal factor (eg, bacterial overgrowth) or a reduced or damaged mucosal surface area (eg, from surgical resection or celiac disease), urinary excretion will be lower than normal. Cases of pancreatic insufficiency usually result in normal urinary excretion because absorption of D-xylose is still intact.

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