The double sugar test of intestinal permeability in the elderly.

Tests of intestinal permeability are used as a reflection of upper-small-intestinal mucosal damage. Thirty-two elderly in-patients aged 75-96 years, and 64 hospital volunteers aged 22-64 years with no overt gastro-intestinal disease were studied to determine whether permeability changes with increasing age. Intestinal permeability was assessed by measuring the 5-h urinary excretion of a monosaccharide, L-rhamnose, and a disaccharide, cellobiose, for 5 h after their oral administration in a hypertonic solution. While in the elderly, excretion of both mono- and di-saccharides was significantly reduced by a half to two-thirds, the ratio of the two sugars in the urine was similar in both age groups. We conclude that permeability was unimpaired in the elderly patients whom we studied. Because the test depends on a ratio of excretion rates rather than an absolute rate, accuracy of urine collection and abnormal renal function do not invalidate the results. It is therefore useful as a screening test of upper-small-intestinal mucosal damage in the elderly.