Modulation of the postprandial acid and bile pockets at the gastro-oesophageal junction by drugs that affect gastric motility

Pathophysiology of gastro-oesophageal reflux disease: implications for diagnosis and management

Gastro-oesophageal reflux disease (GERD) is a common gastrointestinal disorder in which retrograde flow of gastric content into the oesophagus causes uncomfortable symptoms and/or complications. It has a multifactorial and partially understood pathophysiology. GERD starts in the stomach, where the refluxate material is produced. Following the trajectory of reflux, the failure of the antireflux barrier, primarily the lower oesophageal sphincter and the crural diaphragm, enables the refluxate to reach the oesophageal lumen, triggering oesophageal or extra-oesophageal symptoms. Reflux clearance mechanisms such as primary and secondary peristalsis and the arrival of bicarbonate-rich saliva are critical to prevent mucosal damage. Alterations of the oesophageal mucosal integrity, such as macroscopic oesophagitis or microscopic changes, determine the perception of symptoms. The intensity of the symptoms is affected by peripheral and central neural and psychological mechanisms. In this Review, we describe an updated understanding of the complex and multifactorial pathophysiology of GERD. It is now recognized that different GERD phenotypes have different degrees of reflux, severity of mucosal integrity damage and type, and severity of symptoms. These variations are probably due to the occurrence of a predominant pathophysiological mechanism in each patient. We also describe the main pathophysiological mechanisms of GERD and their implications for personalized diagnosis and management.

Effect of hiatus hernia on reflux patterns and mucosal integrity in patients with non-erosive reflux disease

BACKGROUND

Hiatus hernia (HH) contributes to development of gastroesophageal reflux disease, Barrett's esophagus and esophageal adenocarcinoma. This study was aimed to investigate the influence of HH on reflux patterns and distal esophageal mucosal integrity in non-erosive reflux disease (NERD).

METHODS

We retrospectively analyzed PPI-refractory NERD patients referred to three tertiary referral centers who underwent high-resolution manometry and off-PPI 24-h impedance-pH monitoring (with or without bile spectrophotometry). Patients with HH ≥2 cm (HH group, n = 42) or no HH (non-HH group, n = 40) with similar esophageal acid exposure time (AET 6%-12%) were included.

KEY RESULTS

Age, gender, BMI, esophageal motility, AET, and esophageal clearance were similar between the two groups. The HH group had higher numbers of total reflux episodes (p = 0.015) with similar proportion of acid/non-acid reflux compared with the non-HH group. Mean nocturnal baseline impedance (MNBI) in the distal esophagus was significantly lower in the HH group than the non-HH group at both 5 cm (p = 0.002) and 3 cm (p = 0.015) above the lower esophageal sphincter. Multivariable regression analysis showed that HH, less non-acid reflux and lower post-reflux swallow-induced peristaltic wave index (PSPWI) were independently associated with lower MNBI. Among 31 patients tested with bile spectrophotometry, the HH group had significantly longer bile exposure time than the non-HH group (p = 0.011), and bile reflux inversely and significantly correlated with MNBI (rho = -0.75, p < 0.001).

CONCLUSIONS AND INFERENCES

Hiatus hernia, less non-acid reflux and lower PSPWI were associated with lower MNBI. HH impairs distal esophageal mucosal integrity, the mechanism of which we speculate to be through excessive bile reflux.

Evaluations of Gastric Acid Pocket Using Novel Vertical 8-Channel pH Monitoring System and Effects of Acid Secretion Inhibitors

Background/Aims

The gastric acid pocket has an important role in gastroesophageal reflux disease development. In this study, we utilized a novel 8-channel pH monitoring system with sensor intervals of 1 cm on the vertical axis for evaluation of postprandial gastric acid pocket in healthy Japanese adults, as well as the effects of vonoprazan and rabeprazole.

Methods

Twelve healthy volunteers without Helicobacter pylori infection were enrolled. A catheter was inserted transnasally and positioned under X-ray guidance, then postprandial acid pocket formation was monitored over time in a sitting position. Thereafter, acid pocket changes were assessed following administration of vonoprazan (20 mg) or rabeprazole (20 mg).

Results

The gastric acid pocket was successfully measured by use of the present system in 10 cases, while failure occurred in 2 because of inappropriate catheter positioning. Observed acid pockets were visualized with a mean length of 2.2 ± 0.4 channels on the top layer of food contents approximately 20 minutes after finishing a meal. There were some variations for lasting time of the acid pocket. Complete elimination within 3 hours after administration of vonoprazan was noted in all cases. Likewise, following administration of rabeprazole, the acid pocket was eliminated in 7 cases, while acidity was reduced though the pocket remained observable in 3.

Conclusions

Gastric acid pocket observations were possible using our novel vertical 8-channel sensor catheter. The present findings showed that vonoprazan strongly suppressed acid secretion within a short period, suggesting its effectiveness for gastroesophageal reflux disease treatment.

Postprandial proximal gastric acid pocket and its association with gastroesophageal acid reflux in patients with short-segment Barrett's esophagus

OBJECTIVE

To determine the characteristics of postprandial proximal gastric acid pockets (PPGAPs) and their association with gastroesophageal acid reflux in patients with Barrett's esophagus (BE).

METHODS

Fifteen patients with BE (defined by columnar lined esophagus of ≥1 cm) and 15 healthy individuals that were matched for age, gender, and body mass index, were recruited. The fasting intragastric pH and the appearance time, length, lowest pH, and mean pH of the PPGAP were determined using a single pH electrode pull-through experiment. For BE patients, a gastroesophageal reflux disease questionnaire (GerdQ) was completed and esophageal 24-h pH monitoring was carried out.

RESULTS

The PPGAP was significantly longer (5 (3, 5) cm vs. 2 (1, 2) cm) and the lowest pH (1.1 (0.8, 1.5) vs. 1.6 (1.4, 1.9)) was significantly lower in patients with short-segment BE than in healthy individuals. The PPGAP started to appear proximally from the gastroesophageal pH step-up point to the esophageal lumen. The acidity of the PPGAP was higher in the distal segment than in the proximal segment. In short-segment BE patients, there were significant correlations between the acidity and the appearance time and length of the PPGAP. The length and acidity of the PPGAP were positively associated with gastroesophageal acid reflux episodes. The acidity of the PPGAP was associated with the DeMeester scores, the GerdQ scores, and the fasting intragastric pH.

CONCLUSIONS

In patients with short-segment BE, a PPGAP is commonly seen. Its length and acidity of PPGAP are associated with gastroesophageal acid reflux, the DeMeester score, and the GerdQ score in patients with short-segment BE.

The Characteristics of Postprandial Proximal Gastric Acid Pocket in Gastroesophageal Reflux Disease

Background

Postprandial proximal gastric acid pocket (PPGAP) plays important roles in gastroesophageal reflux disease (GERD). In this study, we analyzed the characteristics of PPGAP in GERD.

Material/Methods

There were 17 normal participants and 20 GERD patients who completed a gastroesophageal reflux disease questionnaire (GerdQ) and underwent a gastroscopy, a high-resolution manometry, an esophageal 24-hour pH monitoring, and a station pull-through pH monitoring to assess their symptomatic degree, endoscopic change, acid exposure, and PPGAP.

Results

PPGAP was present in all participants. Compared with normal participants, the PPGAP in GERD patients was significantly different, thus the disappearing time was significantly later (p<0.001), the lasting time was significantly longer (p<0.001), the length was significantly longer (p<0.001), and the lowest pH and the mean pH were significantly lower (p<0.001). The length of PPGAP in GERD patients was positively correlated with GerdQ score (p<0.05). The disappearing time, the lasting time, and the length of PPGAP in GERD patients was positively correlated with the DeMeester score (p<0.01). The lowest pH and the mean pH of PPGAP in GERD patients was negatively correlated with the DeMeester score (p<0.001).

Conclusions

PPGAP was generally present. PPGAP in GERD patients had characteristics of long time period, long length, and high acidity. Its length was positively correlated with subjective symptomatic degree. Its period, length, and acidity were positively correlated with the objective acid exposure. PPGAP seems to be the originator of acid reflux events and plays important roles in GERD.

The Gastric Acid Pocket (or Coat) and Its Attenuation in Helicobacter pylori-infected Subjects

In 2001, it was observed that the cardia region of the lumen of the stomach remained highly acidic after a meal and escaped the buffering effect of the food. This phenomenon was termed the acid pocket and is thought to explain why reflux symptoms occur after meals despite the buffering effect of food. This review describes the discovery of the acid pocket and our progress in understanding the intragastric physiology producing it, its exaggeration in hiatus hernia and role in reflux disease. The recent discovery that the acid pocket is attenuated in the Helicobacter pylori-infected population and the significance of this to the negative association between H. pylori and reflux disease and its complications is also addressed. Finally, the role of the acid pocket in providing protection from potentially pathogenic ingested microorganisms is discussed.

Protective Roles of N-acetyl Cysteine and/or Taurine against Sumatriptan-Induced Hepatotoxicity

Purpose: Triptans are the drug category mostly prescribed for abortive treatment of migraine. Most recent cases of liver toxicity induced by triptans have been described, but the mechanisms of liver toxicity of these medications have not been clear. Methods: In the present study, we obtained LC₅₀ using dose-response curve and investigated cell viability, free radical generation, lipid peroxide production, mitochondrial injury, lysosomal membrane damage and the cellular glutathione level as toxicity markers as well as the beneficial effects of taurine and/or N-acetyl cysteine in the sumatriptan-treated rat parenchymal hepatocytes using accelerated method of cytotoxicity mechanism screening. Results: It was revealed that liver toxicity induced by sumatriptan in in freshly isolated parenchymal hepatocytes is dose-dependent. Sumatriptan caused significant free radical generation followed by lipid peroxide formation, mitochondrial injury as well as lysosomal damage. Moreover, sumatriptan reduced cellular glutathione content. Taurine and N-acetyl cysteine were able to protect hepatocytes against sumatriptan-induced harmful effects. Conclusion: It is concluded that sumatriptan causes oxidative stress in hepatocytes and the decreased hepatocytes glutathione has a key role in the sumatriptan-induced harmful effects. Also, N-acetyl cysteine and/or taurine could be used as treatments in sumatriptan-induced side effects.

Effect of baclofen on gastric acid pocket in subjects with gastroesophageal reflux disease symptoms

Postprandial gastroesophageal reflux (PGER) in the distal esophagus (DE) is associated with a gastric juice 'acid pocket' (AP). Baclofen reduces AP extension into the DE in healthy volunteers, in part through increased lower esophageal sphincter (LES) pressure. We aimed to verify whether baclofen also affects postprandial AP location and extent in gastroesophageal reflux disease (GERD) patients. Thirteen treatment-naive heartburn-prevalent GERD patients underwent two AP studies, after pretreatment with baclofen 40 mg or placebo 30 minutes preprandially. We performed pH-probe stepwise pull-throughs (PT) (1 cm/min, LES -10 to +5 cm) before and every 30 minutes from 30 minutes before up to 150 minutes after a test meal. After the meal, both after placebo and baclofen, gastric pH significantly dropped at 30, 60, 90 minutes postprandially (P: nadir pHs of 3.9 ± 0.6, 2.3 ± 0.6, 2.1 ± 0.4; B: nadir pHs of 2.5 ± 0.4, 2.8 ± 0.4, 2.5 ± 0.3; all P < 0.05). After placebo, LES pressure decreased at 60, 90 and 120 minutes postprandially (32.7 ± 6.1 vs. 24.5 ± 3.1, 27.3 ± 5.9, 27.3 ± 6.0 mmHg; analysis of variance [ANOVA], P = 0.037), but this was prevented by baclofen (25.4 ± 3.4 vs. 29.4 ± 2, 32.2 ± 1.4, 35.5 ± 1.7 mmHg, ANOVA, P = not significant (NS)). Baclofen did not significantly decrease the postprandial AP extent above the LES but prevented the postprandial increase in transient lower esophageal sphincter relaxations (TLESRs) (preprandial vs. postprandial, placebo: 1.1 ± 0.3 vs. 3.7 ± 0.7, P < 0.05; baclofen: 1.4 ± 0.4 vs. 2 ± 0.5, P = NS). In GERD patients, baclofen significantly increases postprandial LES pressure, prevents the increase TLESRs but, unlike in healthy volunteers, does not affect AP extension into the DE.

The Role of the Acid Pocket in Gastroesophageal Reflux Disease

Gastroesophageal reflux disease is one of the commonest chronic conditions in the western world and its prevalence is increasing worldwide. The discovery of the acid pocket explained the paradox of acid reflux occurring more frequently in the postprandial period despite intragastric acidity being low due to the buffering effect of the meal. The acid pocket was first described in 2001 when it was detected as an area of low pH immediately distal to the cardia using dual pH electrode pull-through studies 15 minutes after a meal. It was hypothesized that there was a local pocket of acid close to the gastroesophageal junction that escapes the buffering effect of the meal, and that this is the source of postprandial acidic reflux. The presence of the acid pocket has been confirmed in other studies using different techniques including high-resolution pHmetry, Bravo capsule, magnetic resonance imaging, and scintigraphy. This review aims to describe what we know about the acid pocket including its length, volume, fluid constituents, and its relationship to the lower esophageal sphincter and squamocolumnar junction. We will discuss the possible mechanisms that lead to the formation of the acid pocket and examine what differences exist in patients who suffer from acid reflux. Treatments for reflux disease that affect the acid pocket will also be discussed.

Effect of baclofen on the acid pocket at the gastroesophageal junction

Previous studies established that a pocket of highly acidic gastric juice is present postprandially at the gastroesophageal junction in man. The GABA-B agonist baclofen inhibits postprandial reflux events through its effects on the lower esophageal sphincter (LES). The aim of the current study was to investigate whether baclofen would affect the location and the extent of the postprandial acid pocket in healthy volunteers. Twelve healthy volunteers underwent acid pocket studies on two different occasions, at least 1 week apart. LES position was determined preprandially with pull-through manometry. Dual pH electrode and manometry probe stepwise pull-through (1 cm/minute, LES-10 to +5 cm) was performed at 30-minute intervals for 150 minutes, with administration of placebo or baclofen 40 mg after the first and ingestion of a liquid meal after the second pull-through. After placebo, a significant drop in intragastric gastric pH was present at the gastroesophageal junction after the meal, reflecting the acid pocket, and this was associated with a drop in LES pressure. Baclofen did not affect the presence of the acid pocket, but prevented the postprandial drop in LES pressure, and the extent of the acid pocket above the upper margin of the manometrically located LES was significantly decreased by baclofen (1.6 ± 0.7 vs. 0.3 ± 0.4 cm at 60 minutes, 2.2 ± 0.6 vs. 0.2 ± 0.6 at 90 minutes, and 1.5 ± 0.5 vs. 0.7 ± 0.7 cm at 120 minutes, all P < 0.05). Baclofen does not alter the intragastric acid pocket, but limits its extension into the distal esophagus, probably through an increase in postprandial LES pressure.

Mechanisms of Barrett's oesophagus (clinical): LOS dysfunction, hiatal hernia, peristaltic defects

Barrett's oesophagus, with the potential to develop into oesophageal adenocarcinoma (OAC), is a major complication of gastrooesophageal reflux disease (GORD). However, about 50% of patients developing OAC had no known GORD beforehand. Hence, while GORD symptoms, oesophagitis, and Barrett's have a number of common determinants (oesophagogastric junction (OGJ) incompetence, impaired oesophageal clearance mechanisms, hiatus hernia) they also have some independent determinants. Further, although excess oesophageal acid exposure plays a major role in the genesis of long-segment Barrett's oesophagus there is minimal evidence supporting this for short-segment Barrett's. Hence, these may have unique pathophysiological features as well. Long-segment Barrett's seems to share most, if not all, of the risk factors for oesophagitis, particularly high-grade oesophagitis. However, it is uncertain if OGJ function and acid clearance are more severely impaired in patients with long-segment Barrett's compared to patients with high-grade oesophagitis. With respect to short-segment Barrett's, the acid pocket may play an important pathogenic role. Conceptually, extension of the acid pocket into the distal oesophagus, also known as intra-sphincteric reflux, provides a mechanism or acid exposure of the distal osophageal mucosa without the occurrence of discrete reflux events, which are more likely to prompt reflux symptoms and lead to the development of oesophagitis. Hence, intra-sphincteric reflux related to extension of the acid/no acid interface at the proximal margin of the acid pocket may be key in the development of short segment Barrett's. However, currently this is still somewhat speculative and further studies are required to confirm this.

Effects of baclofen on the functional anatomy of the oesophago-gastric junction and proximal stomach in healthy volunteers and patients with GERD assessed by magnetic resonance imaging and high-resolution manometry: a randomised controlled double-blind study

BACKGROUND

The mechanism of reflux protection may involve a 'flap valve' at the oesophago-gastric junction (OGJ).

AIM

To assess the effects of baclofen, a gamma-aminobutyric acid receptor type-B (GABA-B) agonist known to suppress reflux events, on the 'functional anatomy' of the OGJ and proximal stomach after a large test meal.

METHODS

Twelve healthy volunteers (HVs) and 12 patients with gastro-oesophageal reflux disease (GERD); with erosive oesophagitis or pathological oesophageal acid exposure completed a randomised, double-blind, cross-over study. On 2 test days participants received 40-mg baclofen or placebo before ingestion of a large test meal. OGJ structure and function were assessed by high-resolution manometry (HRM) and magnetic resonance imaging (MRI) using validated methods. Measurements of the oesophago-gastric angle were derived from three-dimensional models reconstructed from anatomic MRI images. Cine-MRI and HRM identified postprandial reflux events. Mixed model analysis and Wilcoxon rank signed tests assessed differences between participant groups and treatment conditions.

RESULTS

In both HVs and GERD patients, baclofen reduced the frequency of postprandial reflux events. The oesophago-gastric insertion angle in GERD patients was reduced (-4.1 ± 1.8, P = 0.025), but was unchanged in healthy controls. In both study groups, baclofen augmented lower oesophageal sphincter (LES) pressure (HVs: +7.3 ± 1.8 mmHg, P < 0.0001, GERD: +4.50 ± 1.49 mmHg, P < 0.003) and increased LES length (HVs: +0.48 ± 0.11 cm, P < 0.0003, GERD: +0.35 ± 0.06 cm, P < 0.0001).

CONCLUSIONS

Baclofen inhibits transient LES relaxations and augments LES pressure and length. Additionally, baclofen has effects on the 'functional anatomy' of the OGJ and proximal stomach in GERD patients, which may suppress reflux by means of a 'flap valve' mechanism.

Gastric acid pocket and gastroesophageal reflux disease

Gastric acid pocket is an area of highly acid that escapes the neutralization of food in the proximal stomach after meals and has been noticed in healthy individuals and gastroesophageal reflux disease (GERD) patients. It was first found by Fletcher et al, who carried out a series of experiments in 2001. After that, other researchers have carried out in-depth studies on it. Hiatus hernia, gastric motility, gastric anatomy and physiology seem to be important elements for the genesis of postprandial proximal gastric acid pocket (PPGAP). Because PPGAP may play an important role in the pathogenesis of GERD, treatments for suppressing the production of gastric acid, antacid agents, prokinetic agents, surgery and other treatments may be used to alter the presence of PPGAP to achieve the purpose of treating GERD. Therefore, the discovery of gastric acid pocket may provide a new idea for the treatment of GERD.

Nonspecific motility disorders, irritable esophagus, and chest pain

This paper presents commentaries on whether Starling's law applies to the esophagus; whether erythromycin affects esophageal motility; the relationship between hypertensive lower esophageal sphincter and vigorous achalasia; whether ethnic- and gender-based norms affect diagnosis and treatment of esophageal motor disorders; health care and epidemiology of chest pain; whether normal pH excludes esophageal pain; the role of high-resolution manometry in noncardiac chest pain; whether pH-impedance should be included in the evaluation of noncardiac chest pain; whether there are there alternative therapeutic options to PPI for treating noncardiac chest pain; and the usefulness of psychological treatment and alternative medicine in noncardiac chest pain.

The acid pocket: a target for treatment in reflux disease?

The nadir esophageal pH of reflux observed during pH monitoring in the postprandial period is often more acidic than the concomitant intragastric pH. This paradox prompted the discovery of the "acid pocket", an area of unbuffered gastric acid that accumulates in the proximal stomach after meals and serves as the reservoir for acid reflux in healthy individuals and gastroesophageal reflux disease (GERD) patients. However, there are differentiating features between these populations in the size and position of the acid pocket, with GERD patients predisposed to upward migration of the proximal margin onto the esophageal mucosa, particularly when supine. This upward migration of acid, sometimes referred to as an "acid film", likely contributes to mucosal pathology in the region of the squamocolumnar junction. Furthermore, movement of the acid pocket itself to a supradiaphragmatic location with hiatus hernia increases the propensity for acid reflux by all conventional mechanisms. Consequently, the acid pocket is an attractive target for GERD therapy. It may be targeted in a global way with proton pump inhibitors that attenuate acid pocket development, or with alginate/antacid combinations that colocalize with the acid pocket and displace it distally, thereby demonstrating the potential for selective targeting of the acid pocket in GERD.

Recent developments in gastroesophageal reflux disease and Barrett's esophagus: ANNO 2012

The incidence of gastroesophageal reflux disease (GERD) and esophageal columnar metaplasia is rising worldwide. Both mechanical and functional factors perturb the double sphincter barrier at the esophagogastric junction (EGJ). Discovery of the acid pocket is fundamental in understanding postprandial acid reflux. Adding impedencemetry to pH measurements allows detection of non-acid or weakly acidic reflux. Histologic and endoscopic injury of the squamous mucosa rises from dilation of the intercellular spaces, papillary extension, accentuated intrapapillary looping, red streaks, erosive tissue loss, etc., graded with the Los Angeles system. Seventy percent of patients have no recognizable abnormalities (non-erosive or neGERD). Treatment of GERD mainly relates to the control of acid secretion but a revival of alginate/antacid obliterating the acid pocket is to be expected. Weaker heartburn control in neGERD is a misnomer because most studies included patients with no evidence of reflux disease. Traditional (delayed-release) proton pump inhibitors (PPIs) are powerful suppressors of acid secretion but do have limitations such as gradual build up of acid control, weak control of nocturnal acid recovery, possibility of rebound, occasional need for dose escalation, etc. Barrett's esophagus (BE) is endoscopically diagnosed also in the absence of intestinal metaplasia. A prerequisite is the precise location of the EGJ (proximal end of gastric folds, esophageal sphincter pinch, distal extent of palisade vessels). BE is graded with the Prague C & M system. Barrett's cancer develops usually via low-grade and high-grade dysplasia. Endoscopic examination may indicate suspicious areas, amenable for targeted biopsy. Otherwise, four quadrant biopsies are obtained when searching for neoplasia. Low-grade dysplasia, especially when it is multifocal and p53 positive, high-grade dysplasia and mucosal cancer should be treated with endoscopic resection of the target area, followed by radiofrequency ablation of the adjacent non-neoplastic columnar mucosa, followed with powerful acid suppressant therapy. The long-term results of the combination of resection and ablation are exiting and at least comparable to surgical resection.

Postprandial proximal gastric acid pocket and gastroesophageal reflux disease

An unbuffered layer of acidity that escapes neutralization by food has been demonstrated in volunteers and gastroesophageal reflux disease patients. This postprandial proximal gastric acid pocket (PPGAP) is manometrically defined by the presence of acid reading (pH<4) in a segment of the proximal stomach between nonacid segments distally (food) and proximally (lower esophageal sphincter or distal esophagus). The PPGAP may have important clinical implications; however, it is still poorly understood. Gastric anatomy and physiology seem to be important elements for PPGAP genesis. Gastric operations and acid suppression medications may decrease distal - proximal intragastric acid reflux and help control gastroesophageal reflux.