Objective: Increased small intestinal permeability has been found in patients with Crohn's disease and in a proportion of their healthy relatives. This may reflect a shared environment or shared genes. The finding of abnormal permeability in the healthy spouses of patients would favor an environmental cause for this observation.
Methods: The healthy spouses of patients with Crohn's disease attending three gastroenterology clinics were invited to participate. Eligible subjects consumed a 350-ml solution containing lactulose, mannitol, and sucrose before bedtime. All overnight urine was collected, assayed by high performance liquid chromatography, and the ratio of fractional excretion of lactulose to mannitol was calculated as an index of permeability. The results were compared with those of a previously determined control group.
Results: Sixty spouses completed the study. Increased permeability was present in eight (13.3%, 95% CI = 6.0-24.6%). The presence of increased permeability was not related to age, gender, duration of cohabitation, alcohol use, nonsteroidal anti-inflammatory drug use or to disease activity in the patient with Crohn's disease. There was a nonsignificant trend for abnormal permeability to occur in those spouses cohabiting with the patient with Crohn's disease at the time of disease diagnosis (p = 0.128).
Conclusions: Small intestinal permeability is increased in a proportion of healthy spouses of patients with Crohn's disease. The presence of abnormal permeability studies in patients with Crohn's disease and a proportion of their healthy close contacts suggests that this phenomenon is caused by environmental factors.