Fecal Calprotectin, Elastase, and Alpha-1-Antitrypsin Levels After Roux-en-Y Gastric Bypass; Calprotectin Is Significantly Elevated in the Majority of Patients.

Background: Roux-en-Y gastric bypass (RYGB) causes several alterations in gastrointestinal function. We hypothesized that levels of three commonly used fecal tests change after RYGB.

Methods: Fecal 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.

Results: Median 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.

Conclusions: Fecal 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.