Running head: Gastric accommodation and motility by MRI and barostat

Background: The barostat is considered the gold standard for evaluation of proximal gastric motility especially for the accommodation response to a meal. The procedure is invasive because it involves the introduction of an intragastric catheter and bag and is not always well tolerated. Moreover, the barostat bag itself may influence motility. Nowadays Magnetic Resonance Imaging (MRI) is able to measure several aspects of gastric motility non-invasively. Aims: To evaluate whether the accommodation response of the stomach, observed with barostat, is present during MRI and whether the barostat interferes with gastric physiology. Materials and Methods: Gastric accommodation, motility and emptying were studied twice in fourteen healthy subjects with MRI using 3D-volume scans and 2Ddynamic scans once in the presence of a barostat bag and once when the barostat bag was not present. Results: Fasting and postprandial intragastric volumes were significantly higher in the experiment with barostat versus without barostat (fasting: 350±132 ml vs. 37±21 ml, p<0.0001, postprandial: 852±126 ml vs. 361±62 ml, p<0.0001). No significant differences were found in gastric emptying (88±41 vs. 9740 ml/h, NS) and contraction frequency between both experiments. The accommodation response observed in the presence of the barostat bag was not observed in the absence of the barostat bag. Conclusions: The presence of an intragastric barostat bag does not interfere with gastric emptying or motility but the accommodation response measured with the barostat in situ is not observed without the barostat bag in situ. Gastric accommodation is a non-physiological barostat-induced phenomenon.