Intestinal permeability in diabetic diarrhoea

Small intestinal permeability to mannitol and lactulose was studied in 12 patients aged 36-70 (mean 56) years with diabetic diarrhoea (DD). Ten uncomplicated diabetics aged 24-56 (mean 37) years and 25 normal subjects aged 22-60 (mean 37) years served as controls. Permeability was assessed by measuring urinary recovery of the test substances after oral ingestion. Mean lactulose excretion in patients with DD was significantly lower than in normal controls but was not significantly different from the uncomplicated diabetics. Mean lactulose excretion was not significantly different in the three groups. However, lactulose to mannitol excretion ratios (LMER) were significantly higher in patients with DD compared to the controls or the uncomplicated diabetics. LMER in seven patients with DD were outside the normal range. LMER in patients with DD did not correlate with blood urea, small intestinal transit time, faecal fat excretion, small intestinal bacterial overgrowth, duration of diabetes or duration of diarrhoea. Jejunal morphology was normal in all patients with DD. It was concluded that small intestinal permeability was abnormal in some patients with DD and that this might be a factor in the aetiology of the diarrhoea.