[Lactose intolerance in chronic inflammatory bowel diseases].

In 124 patients with Crohn's disease (69 women, 55 men; mean age 33.7 [11-66] years) and 53 with ulcerative colitis (30 women, 23 men; mean age 36.2 [19-74] years) the incidence of lactose intolerance, as measured by the H2 breath test and blood sugar concentration, was determined prospectively. To exclude abnormal bacterial colonization of the small intestine or rapid small-intestine transit after partial resection of the small intestine as a cause of lactose intolerance, the oro-caecal transit time for lactulose (H2 breath test) was measured. While 21 of 124 patients with Crohn's disease (16.9%) had the expected incidence of lactose intolerance, this was present in only 2 of 53 patients with ulcerative colitis (3.8%; P < 0.05). The lactose intolerance was independent of the site of any inflammatory changes, disease activity and extent of small-intestine resection. Oro-caecal transit time for lactose was similar for all patients. There was no lactose intolerance in two patients with abnormal small-intestinal bacterial colonization.--Because of their considerable diagnostic and prognostic significance, tests for lactose intolerance should be performed routinely in all cases of Crohn's disease or ulcerative colitis.