Gastric motor and sensory function in health assessed by magnetic resonance imaging: Establishment of reference intervals for the Nottingham test meal in healthy subjects

Quantification of gastric emptying with magnetic resonance imaging in healthy volunteers: A systematic review

BACKGROUND

Several magnetic resonance imaging (MRI) protocols have been used to assess gastric emptying (GE) with MRI. This systematic review summarizes the current literature on the topic. The aim was to provide an overview of the available imaging protocols and underline the items that appear most agreed upon and those that deserve further investigation.

METHODS

According to PRISMA guidelines, two independent reviewers conducted a systematic literature search with a pre-specified strategy in different databases. Peer-reviewed articles that utilized MRI techniques to assess GE in healthy volunteers (HVs) were included. The quality and the outcomes of the studies were reported and analyzed.

KEY RESULTS

The literature search yielded 30 studies (531 HVs, weighted mean age 27.4, weighted mean body mass index 23.0 kg/m² ), T2-weighted sequences, balanced turbo field echo, and balanced gradient echo were evenly utilized, with volunteers in the supine position (74% of the studies). After overnight fasting, both liquid (56%) and mixed (44%) meals were equally utilized. Segmentation of the volumes was predominantly performed manually (63%) with a reported mean T50 ranging from 7 to 330 min.

CONCLUSIONS & INFERENCES

As observed in this systematic review, MRI is a flexible tool for assessing GE. Different protocols were analyzed, showing an equal capacity to assess the GE. However, many items in these protocols still require further investigation to obtain a common standard and increase this assessment quality.

Pilot Double-Blind Randomised Controlled Trial: Effects of Jejunal Nutrition on Postprandial Distress in Diabetic Gastropathy (J4G Trial)

Nausea, vomiting and abdominal pain in diabetic patients are often attributed to diabetic gastropathy (DG). Post-pyloric (“jejunal”) enteral nutrition (JN) may improve nutrition and glycaemia in difficult cases. The acute effects of JN on postprandial symptoms and gastric function in DG patients has not been studied. DG patients with moderate to severe symptoms (gastroparesis cardinal symptom index (GCSI) > 27), diabetic controls without symptoms (DC; GCSI < 14) and healthy controls (HV) were entered into a randomized, double blind controlled trial. JN with liquid nutrient (2 kcal/min) or water was infused for 60 min prior to ingestion of a standardized mixed solid/liquid test meal. Outcomes included postprandial symptoms and effects on gastrointestinal (GI)−peptide hormones and gastric emptying (GE) assessed by magnetic resonance imaging (MRI). Nine DG, nine DC and twelve HV were recruited. DG patients reported more symptoms after meals than other groups (p < 0.05). Post-prandial symptoms were reduced after JN in DG patients (p < 0.01). GE was more rapid after JN in DG and DC patients (p < 0.05). JN induced a GI−peptide response in all subjects; however, this was less pronounced in diabetic groups. JN has beneficial effects on DG patients’ symptoms after a meal. The mechanism is not primarily mediated by effects on GE, but appears to involve other aspects of GI function, including visceral sensitivity.

Non-uniform gastric wall kinematics revealed by 4D Cine magnetic resonance imaging in humans

BACKGROUND

Assessment of gastric function in humans has relied on modalities with varying degrees of invasiveness, which are usually limited to the evaluation of single aspects of gastric function, thus requiring patients to undergo a number of often invasive tests for a full clinical understanding. Therefore, the development of a non-invasive tool able to concurrently assess multiple aspects of gastric function is highly desirable for both research and clinical assessments of gastrointestinal (GI) function. Recently, technological advances in magnetic resonance imaging (MRI) have provided new tools for dynamic (or "cine") body imaging. Such approaches can be extended to GI applications.

METHODS

In the present work, we propose a non-invasive assessment of gastric function using a four-dimensional (4D, volumetric cine imaging), free-breathing MRI sequence with gadolinium-free contrast enhancement achieved through a food-based meal. In healthy subjects, we successfully estimated multiple parameters describing gastric emptying, motility, and peristalsis propagation patterns.

KEY RESULTS

Our data demonstrated non-uniform kinematics of the gastric wall during peristaltic contraction, highlighting the importance of using volumetric data to derive motility measures.

CONCLUSIONS & INFERENCES

MRI has the potential of becoming an important clinical and gastric physiology research tool, providing objective parameters for the evaluation of impaired gastric function.

Gastric accumulation of enteral nutrition reduces pressure changes induced by phasic contractility in an isovolumetric intragastric balloon

BACKGROUND

An isovolumetric intragastric balloon to continuously measure gastric phasic contractility was recently developed by us. We aimed to investigate the readout of this technique in relation to gastric content and gastric emptying.

METHODS

In this crossover investigation, the VIPUN^TM Gastric Monitoring System, which comprises a double lumen nasogastric feeding tube with integrated intragastric balloon, was used to assess phasic gastric contractility by interpretation of the pressure in an isovolumetric balloon in 10 healthy subjects. Balloon pressure was recorded in fasted state, during a 2-hour intragastric nutrient infusion (1 kcal/ml at 25, 75, or 250 ml/h) and 4 hours post-infusion, and quantified as Gastric Balloon Motility Index (GBMI), ranging from 0 (no contractility) to 1 (maximal contractility). Gastric accumulation was quantified with magnetic resonance imaging and gastric emptying with a¹³ C-breath test. Results are expressed as mean(SD).

KEY RESULTS

GBMI was significantly lower during infusion at 250 ml/h compared to baseline (0.13(0.05) versus 0.46(0.12)) and compared to infusion at 25 (0.54(0.21)) and 75 ml/h (0.43(0.20)), all P < 0.005. Gastric content volume was larger after infusion at 250 versus 75 ml/h (P < 0.001). Half-emptying time and accumulation were both negatively correlated with postprandial contractility. Postprandial GBMI was significantly lower when GCV>0 ml compared to when the stomach was empty.

CONCLUSIONS AND INFERENCES

Enteral nutrition dose-dependently decreased the contractility readout. This decrease was linked to gastric accumulation of enteral nutrition.

The Causes of Gastroesophageal Reflux after Laparoscopic Sleeve Gastrectomy: Quantitative Assessment of the Structure and Function of the Esophagogastric Junction by Magnetic Resonance Imaging and High-Resolution Manometry

BACKGROUND

The incidence of de novo gastroesophageal reflux disease (GERD) after LSG is substantial. However, an objective correlation with the structural gastric and EGJ changes has not been demonstrated yet. We aimed to prospectively evaluate the effects of laparoscopic sleeve gastrectomy (LSG) on the structure and function of the esophagogastric junction (EGJ) and stomach.

METHODS

Investigations were performed before and after > 50% reduction in excess body weight (6-12 months after LSG). Subjects with GERD at baseline were excluded. Magnetic Resonance Imaging (MRI), high-resolution manometry (HRM), and ambulatory pH-impedance measurements were used to assess the structure and function of the EGJ and stomach before and after LSG.

RESULTS

From 35 patients screened, 23 (66%) completed the study (age 36 ± 10 years, BMI 42 ± 5 kg/m²). Mean excess weight loss was 59 ± 18% after 7.1 ± 1.7-month follow-up. Esophageal acid exposure (2.4 (1.5-3.2) to 5.1 (2.8-7.3); p = 0.040 (normal < 4.0%)) and reflux events increased after surgery (57 ± 24 to 84 ± 38; p = 0.006 (normal < 80/day)). Esophageal motility was not altered by surgery; however, intrabdominal EGJ length and pressure were reduced (both p < 0.001); whereas the esophagogastric insertion angle (35° ± 11° to 51° ± 16°; p = 0.0004 (normal < 60°)) and esophageal opening diameter (16.9 ± 2.8 mm to 18.0 ± 3.7 mm; p = 0.029) were increased. The increase in reflux events correlated with changes in EGJ insertion angle (p = 0.010). Patients with > 80% reduction in gastric capacity (TGV) had the highest prevalence of symptomatic GERD.

CONCLUSION

LSG has multiple effects on the EGJ and stomach that facilitate reflux. In particular, EGJ disruption as indicated by increased (more obtuse) esophagogastric insertion angle and small gastric capacity were associated with the risk of GERD after LSG. clinicaltrials.gov: NCT01980420.

Feasibility and Safely of Oral Rehydration Therapy before Upper Gastrointestinal Endoscopic Submucosal Dissection

Methods

We used alginade water (125 mL, Nestle Co., Kobe, Japan) for PORT. Alginade water is a flavored sports drink, which is palatable and promotes wound healing due to a high concentration of alginate. We conducted a single-center single-arm prospective feasibility study of PORT in 244 patients who underwent upper gastrointestinal ESD. The group wherein PORT was administered up to two hours before ESD (n = 120) was compared with the historical control group (non-PORT group, n = 120). We investigated the total fluid intake, hematocrit change, complications due to PORT, complications during ESD, ESD procedure time, and length of hospital stay in each group.

Results

The average fluid intake in the PORT group was 462.6 mL. No complications were observed due to PORT and ESD, and significant differences in the ESD procedure time or hospital stay was not noted.

Conclusion

PORT up to two hours before upper gastrointestinal ESD is feasible.

Effects of Laparoscopic Sleeve Gastrectomy on Gastric Structure and Function Documented by Magnetic Resonance Imaging Are Strongly Associated with Post-operative Weight Loss and Quality of Life: a Prospective Study

BACKGROUND

This prospective study applied magnetic resonance imaging (MRI) to assess the effect of laparoscopic sleeve gastrectomy (LSG) on gastric structure and function. The impact of these changes on patient outcomes was analyzed.

METHOD

Obese patients without gastrointestinal symptoms referred for bariatric surgery were recruited prospectively. Pre-operative assessment included (i) high-resolution manometry and pH-impedance monitoring and (ii) magnetic resonance imaging (MRI) measurement of gastric capacity, accommodation, and emptying with the 400 ml liquid Nottingham test meal (NTM). Studies were repeated 6-7 months after LSG. Weight loss and changes in the Gastrointestinal Quality of Life Index (GIQLI) assessed patient outcomes.

RESULTS

From 35 patients screened, 23 (66%) completed the study (17 females, age 36 ± 10 years, BMI 42 ± 5 kg/m2). Mean excess weight loss was 59 ± 18% at follow-up. Total gastric volume (capacity) after the meal was 467 mL (455-585 ml) before and 139 mL (121-185 ml) after LSG (normal reference 534 (419-675) mL), representing a mean 70% reduction (p < 0.0001). Similar findings were present for gastric content volume indicating rapid early-phase gastric emptying (GE) post-LSG. Conversely, late-phase GE was slower post-LSG (2.5 ± 1.0 vs. 1.4 ± 0.6 mL/min; p < 0.0001; (reference 1.5(1.4-4.9) mL/min)). Patients with ≥ 80% reduction in gastric capacity had greater weight loss (p = 0.008), but worse gastrointestinal outcomes (p = 0.023).

CONCLUSIONS

MRI studies quantified the marked reduction in gastric capacity after LSG. The reduction in capacity was associated with rapid early- but slow late-phase GE after surgery. These changes were associated with weight loss; however, reductions in gastric capacity ≥ 80% were linked to increased acid reflux and impacted on gastrointestinal quality of life.

A Method for Multi-day Tracking of Gastrointestinal Smooth Muscle Contractile Patterns in Organotypic Culture

Gastrointestinal (GI) motility is a key component of digestive health, and it is a complex both rhythmic and arrhythmic process governed by many physiological factors. The ability to accurately track the movements of the GI tissues in vitro over multiple days would provide valuable insights into GI tract physiology. A correlational analysis tracking algorithm was developed and applied to intestinal smooth muscle tissues that were maintained in organotypic culture. Physiologically relevant metrics, such as frequency, amplitude and motility index were independently assayed to quantify smooth muscle contractions. The results were validated by manually detected frequency determined using a standard software package. The algorithm was capable of tracking the changes in contractions of the same tissues over six days. This proof-of-concept study demonstrates the feasibility of long-term tracking of GI motility in organotypic cultures over multiple days. The approach allows study of the effects on GI smooth muscle contractility of direct controlled targeting of the cells and molecules in the GI tunica muscularis.

Diabetic Gastroparesis: Perspectives From a Patient and Health Care Providers

Gastroparesis is defined as a delay in gastric emptying in the absence of mechanical obstruction in the stomach. Gastroparesis has a number of causes, including postsurgical, secondary to medications, postinfectious, idiopathic, and as a complication of diabetes mellitus, where it is underrecognized. The cardinal symptoms of diabetic gastroparesis are nausea, early satiety, bloating, and vomiting. Diabetic gastroparesis is more common in females and has a cumulative incidence of 5% in type 1 diabetes and 1% in type 2 diabetes. It is associated with a reduction in quality of life and exerts a significant burden on health care resources. The pathophysiology of this disorder is incompletely understood. Diagnosis is made based on typical symptoms associated with the demonstration of delayed gastric emptying in the absence of gastric outlet obstruction. Gastric emptying scintigraphy is the gold standard for demonstrating delayed gastric emptying, but other methods exist including breath testing and the wireless motility capsule. Diabetic gastroparesis should be managed within a specialist multidisciplinary team, and general aspects involve dietary manipulations/nutritional support, pharmacological therapy, and surgical/endoscopic interventions. Specific pharmacological therapies include prokinetics and antiemetics, with several new medications in the drug development pipeline. Surgical/endoscopic interventions include botulinum toxin injection into the pylorus, gastric peroral endoscopic myotomy and gastric electrical stimulation. This article provides a detailed review and summary of the epidemiology, pathophysiology, investigation, and management of diabetic gastroparesis, and also gives an individual patient's perspective of living with this disabling disorder.

"Development of Fixed Dose Combination Products" Workshop Report: Considerations of Gastrointestinal Physiology and Overall Development Strategy

The gastrointestinal (GI) tract is one of the most popular and used routes of drug product administration due to the convenience for better patient compliance and reduced costs to the patient compared to other routes. However, its complex nature poses a great challenge for formulation scientists when developing more complex dosage forms such as those combining two or more drugs. Fixed dose combination (FDC) products are two or more single active ingredients combined in a single dosage form. This formulation strategy represents a novel formulation which is as safe and effective compared to every mono-product separately. A complex drug product, to be dosed through a complex route, requires judicious considerations for formulation development. Additionally, it represents a challenge from a regulatory perspective at the time of demonstrating bioequivalence (BE) for generic versions of such drug products. This report gives the reader a summary of a 2-day short course that took place on the third and fourth of November at the Annual Association of Pharmaceutical Scientists (AAPS) meeting in 2018 at Washington, D.C. This manuscript will offer a comprehensive view of the most influential aspects of the GI physiology on the absorption of drugs and current techniques to help understand the fate of orally ingested drug products in the complex environment represented by the GI tract. Through case studies on FDC product development and regulatory issues, this manuscript will provide a great opportunity for readers to explore avenues for successfully developing FDC products and their generic versions.