Quantification of Meal Induced Gastric Secretion and Its Effect on Caloric Emptying by Magnetic Resonance Imaging (MRI)

Background: Standard methods for assessment of meal induced gastric secretion are invasive, unphysiological and may themselves alter gastric secretion. Recently, a MRI technique for the quantitative assessment of intragastric secretion and meal dilution was developed [1]. Using this technique and a purpose-built physiologic test meal, this pilot study aimed on the non-invasive quantification of meal induced secretion and its effect on caloric emptying. Methods: Six healthy fasted volunteers (4males, age: 22-45 years (mean 31.8 years), BMI 24.2±1.9 kg/m2) were examined in right lateral position in a 1.5T whole body MRI System after ingestion of a purpose-made, secretogenic test meal. The meal consisted of a 400 ml viscous chocolate drink (450kcal) containing the following ingredients: 90 g carbohydrates, 40 g cacao powder, 100 mg Calcium, 16 g amino acids, 3 g locust bean gum, 133 μl GdDOTA. Gastric content volume (GCV), meal volume (MV) and secretion volume (SV) as well as distribution of secretion were assessed at 10 min intervals for 100 min, whereby MV emptying curves reflected caloric emptying. Previous in-vitro experiments confirmed acid stability and low buffer capacity of the test meal. Data were expressed as means ± SD. Results: The applied test meal continuously stimulated gastric secretion, resulting in a linear SV increase and maximum SV of 240ml at 100min (Figure 1). MV decreased linearly over time with a caloric emptying rate of 1.9±0.3 kcal/min, whereas GCV did not significantly change over time (Figure 1). T50 of caloric emptying was 108±34 min. Mixing of meal and secretion was heterogeneous and an increasing secretion layer on top of the meal was observed. The secretion dynamics resulted in a maximal meal dilution of 48±7 % after 100 min. Caloric emptying rate was negatively correlated to the secretion production rate (r= 0.73, p=0.06). Conclusion: A non-invasive, quantitative MR assessment of gastric secretion volume and distribution of secretions within the stomach is presented. The physiologic test meal induced large volumes of gastric secretion, attaining almost 50% of total gastric content volume at 100min. As a result changes in total gastric content volume (meal and secretion) systematically underestimated meal emptying and, therefore, caloric delivery to the small bowel. These findings highlight the need for concurrent assessment of secretion with gastric content volume if accurate assessment of meal emptying is to be obtained (at least in meals that stimulate secretion). This technique should provide new insight into the effects of acid secretion on gastric function in health and disease (e.g. gastro-esophageal reflux and peptic ulcer disease)” References: 1. Treier et al. JMRI 28:96-102 (2008)