Overview
D xylose absorption test is a diagnostic investigation used to assess intestinal malabsorption. It evaluates the ability of the proximal small intestine, mainly the jejunum, to absorb D xylose, a simple pentose sugar. Since D xylose does not require pancreatic enzymes for absorption and undergoes minimal metabolism, reduced blood or urine levels directly indicate intestinal mucosal damage. The test is mainly used to differentiate malabsorption due to small intestinal mucosal disease from pancreatic insufficiency.
Symptoms
The test is performed in patients presenting with features of malabsorption. Common symptoms include chronic diarrhea, bulky or greasy stools, unintentional weight loss, abdominal distension, fatigue, and nutritional deficiencies. Patients may also show anemia, bone pain, muscle weakness, or delayed growth in children. Persistent gastrointestinal symptoms despite treatment raise suspicion of intestinal malabsorption requiring evaluation with this test.
Causes
Abnormal D xylose test results are caused by impaired absorption from the intestinal mucosa. Low blood and urine D xylose levels suggest mucosal diseases such as celiac disease, tropical sprue, Crohn’s disease, Whipple’s disease, or intestinal infections. Normal D-xylose absorption with ongoing malabsorption symptoms points toward pancreatic insufficiency or bile salt deficiency. Low urine levels with normal blood levels may indicate renal impairment or incomplete urine collection rather than true malabsorption.
Risk Factors
Risk factors for abnormal D xylose absorption include chronic inflammatory bowel disease, gluten-sensitive enteropathy, intestinal infections, prior intestinal surgery, and prolonged diarrhea. Conditions such as renal impairment, severe dehydration, delayed gastric emptying, and bacterial overgrowth can interfere with test accuracy. Use of certain medications and recent antibiotic therapy may also affect results.
Prevention
While intestinal malabsorption cannot always be prevented, early diagnosis using the D-xylose absorption test helps prevent long-term complications such as severe nutritional deficiencies and growth failure. Proper patient preparation, including overnight fasting, adequate hydration, and avoidance of interfering drugs, improves test reliability. Early identification and treatment of underlying intestinal disorders help restore absorption and improve overall patient outcomes.
