Abnormal structure and function of the esophagogastric junction and proximal stomach in gastroesophageal reflux disease.

OBJECTIVES: This study applies concurrent magnetic resonance imaging (MRI) and high-resolution manometry (HRM) to test the hypothesis that structural factors involved in reflux protection, in particular, the acute insertion angle of the esophagus into the stomach, are impaired in gastroesophageal reflux disease (GERD) patients. METHODS: A total of 24 healthy volunteers and 24 patients with mild-moderate GERD ingested a test meal. Three-dimensional models of the esophagogastric junction (EGJ) were reconstructed from MRI images. Measurements of the esophagogastric insertion angle, gastric orientation, and volume change were obtained. Esophageal function was assessed by HRM. Number of reflux events and EGJ opening during reflux events were assessed by HRM and cine-MRI. Statistical analysis applied mixed-effects modeling. RESULTS: The esophagogastric insertion angle was wider in GERD patients than in healthy subjects (+7° ± 3°; P=0.03). EGJ opening during reflux events was greater in GERD patients than in healthy subjects (19.3 mm vs. 16.8 mm; P=0.04). The position of insertion and gastric orientation within the abdomen were also altered (both P<0.05). Median number of reflux events was 3 (95% CI: 2.5-4.6) in GERD and 2 (95% CI: 1.8-3.3) in healthy subjects (P=0.09). Lower esophageal sphincter (LES) pressure was lower (-11 ± 2 mm Hg; P<0.0001) and intra-abdominal LES length was shorter (-1.0 ± 0.3 cm, P<0.0006) in GERD patients. CONCLUSIONS: GERD patients have a wider esophagogastric insertion angle and have altered gastric morphology; structural changes that could compromise reflux protection by the "flap valve" mechanism. In addition, the EGJ opens wider during reflux in GERD patients than in healthy volunteers: an effect that facilitates volume reflux of gastric contents.

Gastroesophageal junction: structure and function as assessed by using MR imaging.

PURPOSE: To develop and validate magnetic resonance (MR) imaging protocols for quantitative assessment of the structural and functional properties of the gastroesophageal junction (GEJ) and to compare MR imaging detection of reflux events against concurrent manometry as a reference method. MATERIALS AND METHODS: The local ethics committee approved this study, and written informed consent was obtained. Twelve healthy volunteers were examined. Three-dimensional models of the GEJ and proximal portion of the stomach were reconstructed from high-spatial-resolution anatomic MR images to assess the insertion angle of the esophagus into the stomach and proximal stomach distention before and after ingestion of a large test meal. A linear mixed-effects model was used to detect differences in the insertion angle and proximal stomach distention with respect to the respiratory cycle and gastric filling. Additionally, dynamic MR imaging at high temporal resolution was used to detect reflux events. RESULTS: The esophageal insertion angle, given in units of plane angle (radians), was more acute in expiration than in inspiration (0.57 vs 0.73 radian, P = .004) but was not affected by feeding. Progressive distention of the proximal stomach was observed from baseline compared with the postprandial period (0.95 vs 0.65 radian(-1), P < .05). Eighteen reflux events detected by using MR imaging were also detected by using manometry. CONCLUSION: MR imaging methods were developed and validated for the assessment of GEJ structure and function (a) to describe the effects of respiration and feeding on the reflux barrier and (b) to detect reflux events in real time. Anatomic and dynamic MR imaging may be useful techniques in the assessment of GEJ physiology and reflux.

Effect of meal volume and calorie load on postprandial gastric function and emptying: studies under physiological conditions by combined fiber-optic pressure measurement and MRI.

This study assessed the effects of meal volume (MV) and calorie load (CL) on gastric function. MRI and a minimally invasive fiber-optic recording system (FORS) provided simultaneous measurement of gastric volume and pressure changes during gastric filling and emptying of a liquid nutrient meal in physiological conditions. The gastric response to 12 iso-osmolar MV-CL combinations of a multinutrient drink (MV: 200, 400, 600, 800 ml; CL: 200, 300, 400 kcal) was tested in 16 healthy subjects according to a factorial design. Total gastric volume (TGV) and gastric content volume (GCV = MV + secretion) were measured by MRI during nasogastric meal infusion and gastric emptying over 60 min. Intragastric pressure was assessed at 1 Hz by FORS. The dynamic change in postprandial gastric volumes was described by a validated three-component linear exponential model. The stomach expanded with MV, but the ratio of GCV:MV at t(0) diminished with increasing MV (P < 0.01). Postprandial changes in TGV followed those of GCV. Intragastric pressure increased with MV, and this effect was augmented further by CL (P = 0.02); however, the absolute pressure rise was <4 mmHg. A further postprandial increase of gastric volumes was observed early on before any subsequent volume decrease. This "early" increase in GCV was greater for smaller than larger MV (P < 0.01), indicating faster initial gastric emptying of larger MV. In contrast, volume change during filling and in the early postprandial period were unaffected by CL. In the later postprandial period, gastric emptying rate continued to be more rapid with high MVs (P < 0.001); however, at any given volume, gastric emptying was slowed by higher CL (P < 0.001). GCV half-emptying time decreased with CL at 18 +/- 6 min for each additional 100-kcal load (P < 0.001). These findings indicate that gastric wall stress (passive strain and active tone) provides the driving force for gastric emptying, but distal resistance to gastric outflow regulates further passage of nutrients. The distinct early phase of gastric emptying with relatively rapid, uncontrolled passage of nutrients into the small bowel, modulated by meal volume but not nutrient composition, ensures that the delivery of nutrients in the later postprandial period is related to the overall calorie load of the meal.