Simultaneous administration of lactulose and 51Cr-ethylenediaminetetraacetic acid. A test to distinguish colonic from small-intestinal permeability change.

In normal adults intestinal permeation of ingested 51Cr-ethylenediaminetetraacetic acid (EDTA) is greater than that of lactulose. This difference is abolished in patients with ileostomies, suggesting that it results from colonic permeation of 51Cr-EDTA, which, unlike lactulose, resists bacterial degradation. To investigate the effect of an increase in colonic permeability on absorption of the two molecules, lactulose (5 g) and 51Cr-EDTA (50 microCi) were given orally in isosmolar solution to 11 patients with colitis, and their 24-h urinary excretion measured. By comparison the effect of an increase in small-intestinal permeability induced by ingestion of a hyperosmolar solution (4240 mosm/l) was measured in 10 healthy adults. Hyperosmolar stress increased the 24-h urinary excretion of 51Cr-EDTA above the normal mean + 2 standard deviations (3.31%) in all 10 healthy subjects, and in all of these excretion of lactulose was also increased (greater than 1.06%). In contrast, although seven colitics had a urinary excretion of 51Cr-EDTA above the normal mean + 2 SD, in only two of these patients was recovery of lactulose increased. This suggests that simultaneous administration of lactulose and 51Cr-EDTA may enable permeability changes affecting the colon alone to be distinguished from those involving the small intestine.