Effect of gastric secretion on gastric volume responses, emptying and intragastric dilution in humans – a magnetic resonance imaging (MRI) study

Aims: The formation of unbuffered gastric acid layers by gastric secretions after ingestion of a meal is important for understanding gastroesophageal reflux. Hitherto, a visualization of these phenomena and their relationship to meal and stomach volume was not possible. We have developed a novel T₁ mapping technique allowing the quantitative assessment of dilution processes of meals.

Aims: To evaluate the effect of pentagastrin induced gastric secretion on gastric volume responses and intragastric spatial and temporal dilution of a liquid meal by MRI.

Methods: Using a 1.5T MRI System, 12 volunteers were examined in supine position on two separate days after a 500ml, 200kcal viscous glucose drink labelled with 1200µM Gd-DOTA. The first scan after the meal defines t₀ and starting volume V₀. Placebo (0.9%NaCl) or pentagastrin (0.6µg/kg/h) were administered intravenously at the start of ingestion in double-blind randomized order over 60min. Stomach, meal volumes and gastric secretion by T₁ maps were assessed every 5min for 90min. Dynamics of stomach and meal volume change from V₀, described by the parameter κ, and half emptying times (T₅₀) were quantified. The amplitude of volume changes was measured by area under the curve during infusions (AUC_inf).

Results: Fasting and initial postprandial gastric volumes were similar in both conditions (p>0.05). Pentagastrin increased stomach and meal volumes during infusion, whereas volumes immediately decreased for placebo (κ: 1.7±0.06 vs. 1.0±0.05, p<0.001). κ values were similar for stomach and meal volume curves in both conditions (p>0.05). T₅₀ was higher for pentagastrin than for placebo (T₅₀ meal: 84±7 vs. 56±4min, p<0.001). The increase of T₅₀ was associated with AUC_inf (R²=0.73, p<0.001). Pentagastrin infusion caused distinct intraluminal fluid layering only seen on T₁ maps on the top of the meal extending from the gastric fundus to the antrum with a dilution ratio of 1:3.

Conclusions: T₁ mapping visualizes and quantifies layers of secretion on intragastric contents. This could be the anatomic correlate for multilayered gastric acid distribution reported previously. Changes in meal volumes due to gastric secretion are major determinants of stomach volume responses and gastric emptying.