Evaluation of the Lactulose/Mannitol and ⁵¹Cr-Ethylenediaminetetraacetic Acid/¹⁴C-Mannitol Methods for Intestinal Permeability: Influence of Urinary Volume, Sex, Age, Smoking, and Intestinal Disease on Marker Excretion

Abstract

Background: We earlier compared the lactulose/mannitol and ⁵¹Cr-ethylenediaminetetraacetic acid (EDTA)/¹⁴C-mannitol methods for intestinal permeability We have now investigated an increased number of control subjects, with special regard to the influence of urinary volume, sex, age, and smoking on marker excretion, and patients with intestinal disorders, with special regard to correlations between markers. Methods: The 0- to 6-h urinary excretion of orally administered markers was measured in 65 control subjects and in 70 patients. Results: In the control group excretion of mannitol and ¹⁴C-mannitol (small-pore permeability markers) was strongly correlated to urinary volume, whereas such correlation was weak for lactulose and absent for ^5lCr-EDTA (large-pore permeability markers). No sex difference in marker excretion was found, but correlation to urinary volume was more pronounced in males. There was a slightly decreasing excretion of markers with increasing age, reaching significance for ^5lCr-EDTA and ^l4C-mannitol; their excretion ratio was unaffected. Smoking did not significantly affect marker excretion. In the patient group the excretion of large-pore markers tended to be higher and that of small-pore markers to be lower than in the control group; correlation between the large-pore markers, between the small-pore markers, and between the large-pore/small-pore marker ratios was higher than in the control group. Conclusions: Correction for urinary volume substantially reduces variability in small-pore marker excretion. Excretion of both types of markers tends to decrease with age, the large-pore/small-pore marker ratio remaining unchanged. Smoking does not affect small-intestinal permeability. ¹⁴C-mannitol is preferred to chemically determined mannitol owing to lower test variability.

Key Words:

• ⁵¹Cr-Ethylenediaminetetraacetic acid
• intestinal absorption
• intestinal permeability
• lactulose
• mannitol
• ¹⁴C-mannitol