BackgroundRoux-en-Y gastric bypass (RYGB) causes several alterations in gastrointestinal function. We hypothesized that levels of three commonly used fecal tests change after RYGB.MethodsFecal levels of calprotectin, elastase, and alpha-1-antitrypsin were determined in 122 patients without signs of gastrointestinal disease 1 to 2 years after RYGB. Medians, distribution of values, and the percentage of patients with levels above or below reference values were determined.ResultsMedian fecal calprotectin level was 163.5 (<30–1587) μg/g; in 87 % of patients, it was above the reference value (<50 μg/g). Median fecal elastase level was 444 (<15–647) μg/g; 13 % was below the reference value (>200 μg/g). Median fecal alpha-1-antitrypsin level was 0.51 (<0.20–2.20) mg/g, comparable to the reference values.ConclusionsFecal calprotectin levels are significantly higher than the reference value in most patients after RYGB. Fecal elastase is significantly lower. This might indicate that the validity of fecal calprotectin testing is impaired after RYGB and the specificity for fecal elastase is decreased. Clinical awareness of altered fecal markers after RYGB is essential to prevent unnecessary diagnostic tests, such as colonoscopy. Fecal alpha-1-antitrypsin is not influenced by RYGB.

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Background: Roux-en-Y gastric bypass (RYGB) can cause multiple food intolerances and gastrointestinal complaints are frequently reported after dairy consumption. We aimed to determine the prevalence of lactose malabsorption and intolerance, and complaints associated with dairy consumption in daily life, before and after RYGB. Method: The lactose breath test (LBT) and lactose tolerance test (LTT) was performed in 84 patients awaiting RYGB surgery and 84 patients after surgery. Gastrointestinal symptoms at baseline and after testing were recorded. Lactose malabsorption was defined as a positive LBT and/or LTT. Lactose intolerance as a positive test combined with an increase of gastrointestinal complains. Dairy consumption in daily life and successive gastrointestinal complaints were registered via a questionnaire. Results of preoperative and postoperative patients were compared. Results: Lactose malabsorption was present in 15 (17.9%) of the preoperative patients and in 25 (29.8%) of the postoperative patients (OR 2.46; 95%CI: 1.08-5.59; p ¼ .03). Of the preoperative patients 6 (7.1%) patients met the criteria for lactose intolerance, compared to 8 (9.5%) patients in the postoperative group (OR 1.48; 95%CI 0.48-4.57; p ¼ .50). Twelve (14.3%) preoperative patients indicated to have gastrointestinal complaints after dairy consumption in daily life versus 45 (53.6%) postoperative patients (p < .01). Conclusion: This study shows no increase in patients with proven lactose intolerance after RYGB compared to preoperative patients. Gastrointestinal complaints after dairy consumption in daily life were far more frequently reported by RYGB patients. It is unlikely that all reported gastrointestinal complaints are actually caused by lactose. Other ingredients in dairy, like fat, are possibly contributory.

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