Evaluation of gastric emptying measured with the 13C-octanoic acid breath test in patients with functional dyspepsia comparison with ultrasonography

Background: As a non-invasive modality by which to evaluate the gastric emptying of a solid meal, the C-13-octanoic acid breath test has recently become more widely used. Previously, we reported that ultrasonography was another non-invasive and reliable method for assessing gastric motility. The aim of this study was to compare the reliability of these two methods. Methods: Seventeen patients with functional dyspepsia and 10 healthy volunteers were studied. The solid test meal consisted of a scrambled egg labeled with C-13-octanoic acid (100 mg) and served with a bowl of rice and boiled chicken (total 424 kcal). After ingestion of the test meal, all subjects were examined in the sitting position. Ultrasonograph y images were obtained every 15 min for 3 h. Breath sampling followed the same time schedule as for the ultrasonography, with an additional 3 h of sampling at 30-min intervals. We investigated the half emptying time (T1/2) and the lag phase with both methods. Results: The T1/2 by the ultrasonography method and the breath test were positively correlated (r(2) = 0.638); however, there was no significant agreement between the study groups. Both the T1/2 and the lag phase were prolonged in the functional dyspepsia patients compared with the healthy volunteers, regardless of the method of measurement. The lag phase was significantly correlated (r(2) = 0.864) with the T1/2 by the breath test. Conclusions: Although the C-13-octanoic acid breath test cannot assess the gastric emptying of solids as reliably as ultrasonography, both tests are useful for evaluating functional dyspepsia patients with delayed gastric emptying.