Lactose intolerance in active Crohn's disease: clinical value of duodenal lactase analysis

Patients with active Crohn's disease (CD) often report having abdominal symptoms after ingestion of milk products, but the pathomechanism for lactose malabsorption seems to be complex.

To investigate the prevalence of clinical milk intolerance and to objectify symptoms with hydrogen (H 2 ) breath testing, analysis of lactase protein, and enzyme activity in the duodenal mucosa in patients with CD and in healthy controls.

In 49 patients with CD and 24 controls, H 2 breath testing was performed. All individuals underwent endoscopy of the upper gastrointestinal tract, in which multiple pinch samples were taken from the distal duodenum. Lactase activity was measured using the method of Dahlquist. The lactase protein expression was analyzed by gel electrophoresis using the monoclonal antibody mlac 10 and by immunochemistry using the monoclonal antibody mlac 4.

Prevalence of milk intolerance in healthy controls was 16.6% versus 46.9% in patients with CD, with a high frequency (83.3%) in patients with active disease (CD activity index >150). Milk intolerance was correlated to the duration of inflammatory bowel disease ( p = 0.023) but not to the location or previous bowel resection. Hydrogen breath testing had a moderate sensitivity in detecting lactose maldigestion (70.4%) and a high specificity (95.6%). Duodenal lactase levels were also correlated to disease activity, whereas correlations to clinical symptoms remained poor. Patients with milk intolerance had a significantly reduced bone density at the lumbar spine (z-score, -1.33 +/- 0.92 vs. -0.19 +/- 0.95 [mean +/- SD]; p = 0.002)

Milk intolerance is a frequent problem in active CD, which can be objectified accurately by H 2 lactose breath testing. Decreased lactase levels in the duodenal mucosa may be found during an acute flare but are not the predominant cause of milk intolerance in CD.