Oral Absorption Tests: Absorption Site of Each Substrate

Three oral absorption tests have been used in patients with short bowel syndrome (SBS) to evaluate the absorption site of each substrate. In this study, three absorption tests were applied: the oral pancreatic function test using N-benzoyl-image-tyrosyl-p-aminobenzoic acid (NBT-PABA), the image-xylose tolerance test, and the oral fat tolerance test. Examinations were performed in eight patients with either a duodenostomy or a jejunostomy located less than 60 cm from the ligament of Treitz, and in a patient with an end ileostomy. Forty-six healthy volunteers participated as controls for the oral fat tolerance test. PABA and image-xylose concentrations were measured in urine. The serum triacylglycerol concentration was determined at 0, 1, 2, and 3 h after ingestion. All eight patients with SBS demonstrated pathologic absorption on each test. We conclude that small bowel integrity is critical for evaluation of the NBT-PABA test. We also determined that the duodenum and proximal jejunum do not play an important role in the absorption of image-xylose and triacylgylcerol. We could also evaluate limitations and advantages of the other kinds of oral absorption tests and nutrients through patients with SBS.