Characterization of cortical potentials evoked by oesophageal balloon distention and acid perfusion in patients with functional heartburn

Gastrointestinal Interoception in Eating Disorders: Charting a New Path

PURPOSE OF REVIEW

Abnormal interoception has been consistently observed across eating disorders despite limited inclusion in diagnostic conceptualization. Using the alimentary tract as well as recent developments in interoceptive neuroscience and predictive processing as a guide, the current review summarizes evidence of gastrointestinal interoceptive dysfunction in eating disorders.

RECENT FINDINGS

Eating is a complex process that begins well before and ends well after food consumption. Abnormal prediction and prediction-error signals may occur at any stage, resulting in aberrant gastrointestinal interoception and dysregulated gut sensations in eating disorders. Several interoceptive technologies have recently become available that can be paired with computational modeling and clinical interventions to yield new insights into eating disorder pathophysiology. Illuminating the neurobiology of gastrointestinal interoception in eating disorders requires a new generation of studies combining experimental probes of gut physiology with computational modeling. The application of such techniques within clinical trials frameworks may yield new tools and treatments with transdiagnostic relevance.

Esophageal mucosal innervation in functional heartburn: Closer to healthy asymptomatic subjects than to non-erosive reflux disease patients

BACKGROUND

Mucosal innervation in non-erosive reflux disease (NERD; pathological esophageal acid exposure, normal macroscopic mucosa) is clearly distinct from that of healthy volunteers (HV) and from patients with esophagitis or Barrett's esophagus: The nerves in NERD are situated much closer to the luminal surface of the mucosa. Patients with functional heartburn (FH) have a similar symptom profile to patients with NERD and indistinguishable macroscopic appearances. However, they have physiological acid exposure and no reflux-symptom association. The aim of our study was to delineate the position of esophageal mucosal nerve fibers in patients with FH and compare it with that in NERD and HV.

METHODS

Distal esophageal biopsies from patients with FH were immunohistochemically stained for CGRP. CGRP-positive nerve fibers were identified, and their position relative to the lumen was determined. These results were compared to our previously published cohort of HV and NERD.

RESULTS

Eleven patients were included in the FH group with a mean age of 46 years (range 33-69); 7F:4M. Nine patients had visible nerve fibers. The location of the afferent nerve fibers in the distal esophageal mucosa (median of 22, range 10.4-28) was similar to the HV group (median 25.5) and significantly deeper than the superficial nerves seen in NERD (median 9.5).

CONCLUSIONS

The mucosal innervation pattern in FH is more alike that of healthy individuals than that of NERD, with afferent nerves lying deep in the mucosa, away from the luminal surface. This supports the theory that heartburn in FH has a distinct nociceptive pathophysiology.

Central sensitization in chronic pain and medically unexplained symptom research: A systematic review of definitions, operationalizations and measurement instruments

OBJECTIVE

Central sensitization (CS), a mechanism explaining the persistence of symptoms, has been the focus of many research projects. Explanations given to patients with chronic pain are often based on this mechanism. It is hypothesized that CS also plays an important role in the persistence of medically unexplained symptoms (MUS). However, definitions and operationalizations of CS vary. We conducted a systematic review of definitions, operationalizations and measurement instruments of CS.

METHODS

We searched in PubMed, EMBASE, PsycINFO, Cinahl and The Cochrane Library till September 2017 and included papers that addressed CS in relation to chronic pain and/or MUS. Two reviewers independently selected, analysed and classified information from the selected publications. We performed a thematic analysis of definitions and operationalizations. We listed the measurement instruments.

RESULTS

We included 126 publications, 79 publications concerned chronic pain, 47 publications concerned MUS. Definitions of CS consistently encompass the theme hyperexcitability of the central nervous system (CNS). Additional themes are variably present: CNS locations, nature of sensory input, reduced inhibition and activation and modulation of the NDMA receptor. Hyperalgesia and allodynia are widely mentioned as operationalizations of CS. Quantitative sensory testing (QST) and (f)MRI are the most reported measurement instruments.

CONCLUSIONS

There is consensus that hyperexcitability is the central mechanism of CS. Operationalizations are based on this mechanism and additional components. There are many measurement instruments available, whose clinical value has still to be determined. There were no systematic differences in definitions and operationalizations between the publications addressing MUS and those addressing chronic pain.

Comparison of Esophageal Function Tests in Chinese Patients with Functional Heartburn and Reflux Hypersensitivity

OBJECTIVE

To investigate the differences in the results of esophageal function tests for functional heartburn (FH) and reflux hypersensitivity (RH).

METHODS

Patients with FH and RH and healthy volunteers (HVs) from the Department of Gastroenterology, Beijing Anzhen Hospital and Beijing Chao-Yang hospital, who underwent high-resolution manometry and impedance (HRIM), and 24-hour multichannel intraluminal impedance and pH recording (MII/pH) between 2014 and 2016, were enrolled in this study.

RESULTS

36 HV, 147 FH patients, and 91 RH patients were enrolled. The postreflux swallow-induced peristaltic wave index (PSPW index) and mean nocturnal baseline impedance (MNBI) values were significantly lower in RH than in FH and HV. The ineffective esophageal motility (IEM), fragmented peristalsis rates, total bolus exposure, proximal total reflux events, and distal total reflux events were significantly greater in RH than in FH and HV.

CONCLUSIONS

Compared to HV and FH patients, RH patients exhibited greater IEM and fragmented peristalsis rates, a greater total bolus exposure, more proximal total and distal total reflux events, and reduced chemical clearance and mucosal integrity. By using the above described parameters, HRIM and MII/pH assays could be used to correctly classify RH and FH and hence allow physicians to provide adequate relief from associated symptoms.

The Role of Esophageal Hypersensitivity in Functional Heartburn

Functional heartburn (FH) is defined as a functional esophageal disorder characterized by symptoms of chronic heartburn with no apparent correlation to acid or nonacid reflux. In addition, its symptoms persist despite the lack of organic abnormalities or inflammation, esophageal motility disorders, or metabolic disorders. Although conditions presenting with esophageal symptoms without endoscopic abnormalities were previously categorized as nonerosive reflux disease, such conditions are now classified into 3 categories under Rome IV criteria: nonerosive reflux disease, reflux hypersensitivity, and FH. Although many aspects of FH remain unclear, its onset mechanism is considered to be strongly associated with peripheral or central sensitization, given the fact that its symptoms seem to be unrelated to gastroesophageal reflux. In addition, the cause of such hypersensitivity is an interesting topic in itself, and psychological factors, such as stress followed by increasing esophageal permeability are gaining attention as factors that can potentially influence this condition. There is a great unmet clinical need for therapeutic drugs that can be used to treat FH, and the development of novel drugs, diagnostic tests and biomarkers is eagerly awaited.

Esophageal acid sensitivity and mucosal integrity in patients with functional heartburn

BACKGROUND

Patients with functional heartburn (FH) experience troublesome heartburn that is not related to gastroesophageal reflux. The etiology of the heartburn sensation in FH patients is unknown. In patients with reflux disease, esophageal hypersensitivity seems associated with impaired mucosal integrity. We aimed to determine esophageal sensitivity and mucosal integrity in FH and non-erosive reflux disease (NERD) patients.

METHODS

In this prospective experimental study, we performed an acid perfusion test and upper endoscopy with biopsies in 12 patients with NERD and nine patients with FH. Mucosal integrity was measured during endoscopy using electrical tissue impedance spectroscopy and biopsy specimens were analyzed in Ussing chambers for transepithelial electrical resistance and transepithelial permeability.

KEY RESULTS

Lag time to heartburn perception was significantly longer in FH patients (median 12 min) than in NERD patients (median 3 min). Once perceived, intensity of heartburn was scored equal with median visual analog scale 6.5 and 7.1 respectively. Esophageal mucosal integrity was also comparable between FH and NERD patients, both in vivo extracellular impedance and ex vivo transepithelial resistance and permeability were similar.

CONCLUSIONS & INFERENCES

Patients with FH did not show acid hypersensitivity as seen in patients with NERD. However, once perceived, intensity of heartburn is similar. Esophageal mucosal integrity is similar between NERD and FH patients, and is therefore unlikely to be the underlying cause of the observed difference in esophageal acid perception.

Gastroesophageal reflux disease-related and functional heartburn: pathophysiology and treatment

PURPOSE OF REVIEW

Patients who continue to experience heartburn symptoms despite adequate-dose proton pump inhibitor therapy have unmet clinical needs. In this review, we focus on the most recent findings related to the mechanism of heartburn symptom generation, and on the treatment of gastroesophageal reflux disease-related and functional heartburn.

RECENT FINDINGS

The immunological mechanism in the esophageal mucosa has been addressed as a potential mechanism of the onset of esophageal mucosa damage and the generation of heartburn symptoms. Peripheral or central hypersensitivity in viscera is a potentially unifying pathophysiological concept in functional heartburn. Vonoprazan, a novel and potent first-in-class potassium-competitive acid blocker, is expected to prove useful in the treatment of reflux disease.

SUMMARY

New findings in the mechanisms of heartburn symptom generation are emerging, including the immunological mediation of esophageal mucosal damage and the development of visceral hypersensitivity in functional heartburn. In the future, we anticipate the emergence of new and specific therapeutic options based on these mechanisms, with less dependence on acid-suppressing agents.

Role of 5-HT1A receptor in insular cortex mediating stress - induced visceral sensory dysfunction

BACKGROUND

5-HT1A receptors (HTR1As) in the insular cortex are thought to be related with the generation of stress-induced functional gastrointestinal disorders (FGIDs), but its mechanism is not clear. Visceral hypersensitivity is one important pathophysiological mechanism of FGIDs. This study aimed to explore the role of HTR1As in mediating stress-induced visceral hypersensitivity and its mechanism in the insular cortex.

METHODS

Visceral hypersensitivity rat model was established by water avoidance stress (WAS) and the visceral sensitivity was measured by electromyogram. The activities of HTR1As were regulated by microinjecting the HTR1A agonist and antagonist into the insular cortex. The expression levels of 5-HT, HTR1A, N-methyl-d-aspartic acid receptor subtype 2B (NR2B) and c-fos were observed by RT-PCR, Western Blot and immunohistochemical staining.

KEY RESULTS

In WAS rats, the expression levels of 5-HT and HTR1As in the insular cortex were significantly lower (p < 0.05) than that in sham WAS and normal rats, but the levels of c-fos and NR2B were significantly higher (p < 0.05). After microinjecting HTR1As agonist into the insular cortex of WAS rats, the visceral sensitivity and the expression levels of NR2B and c-fos in insular cortex significantly decreased (p < 0.05).

CONCLUSIONS & INFERENCES

The HTR1As-NR2B signal pathway of insular cortex plays an important role in regulating stress-induced visceral hypersensitivity.

Diagnosis and Management of Functional Heartburn

Heartburn is among the most common gastrointestinal symptoms presenting to both generalist physicians and gastroenterologists. Heartburn that does not respond to traditional acid suppression is a diagnostic and therapeutic dilemma. In the era of high utilization of proton pump inhibitors, a substantial proportion of patients presenting to the gastroenterologist with chronic symptoms of heartburn do not have a reflux-mediated disease. Subjects without objective evidence of reflux as a cause of their symptoms have "functional heartburn". The diagnostic role of endoscopy, reflux and motility testing in functional heartburn (FH) patients is discussed. Lifestyle modifications, pharmacological interventions, and alternative therapies for FH are also presented. Recognition of patients with FH allows earlier assignment of these patients to different treatment algorithms, which may allow greater likelihood of success of treatment, diminished resource utilization and improved quality of life. Further data on this large and understudied group of patients is necessary to allow improvement in treatment algorithms and a more evidence-based approach to care of these patients.

Central response to painful electrical esophageal stimulation in well-defined patients suffering from functional chest pain

BACKGROUND

Functional chest pain (FCP) of presumed esophageal origin is considered a common cause for chest pain in which central nervous system hyperexcitability is thought to play an important role. We aimed to compare cerebral responses with painful esophageal stimuli between FCP patients and healthy subjects (HS).

METHODS

Thirteen patients with FCP (seven females, mean age 50.4 ± 7.5 years) and 15 HS (eight females, mean age 49.1 ± 12.9 years) were enrolled. Inclusion criteria consisted of typical chest pain, normal coronary angiogram, and normal upper gastrointestinal evaluation. Electrical stimulations evoking the pain threshold were applied in the distal esophagus, while cortical evoked potentials were recorded from the scalp. Pain scores, resting electroencephalogram (EEG), evoked potential characteristics and brain electrical sources to pain stimulation were compared between groups.

KEY RESULTS

No differences were seen between patients and HS regarding (i) pain thresholds (patients: 20.1 ± 7.4 mA vs HS: 22.4 ± 8.3 mA, all P > 0.05), (ii) resting-EEG (P > 0.05), (iii) evoked brain potential latencies (N2: patients 181.7 ± 25.7 mS vs HS 182.2 ± 25.8 mS, all P > 0.05) and amplitudes (N2P2: patients 8.2 ± 7.2 μV vs HS: 10.1 ± 3.4 μV, all P > 0.05), (iv) topography (P > 0.05), and (v) brain source location (P > 0.05).

CONCLUSIONS & INFERENCES

No differences in activation of brain areas to painful esophageal stimulation were seen in this group of well characterized patients with FCP compared with sex- and age-matched HS. The mechanism of pain in FCP and whether it originates in the esophagus remains unsolved.

Overlap of functional heartburn and gastroesophageal reflux disease with irritable bowel syndrome

Several studies indicate a significant degree of overlap between irritable bowel syndrome (IBS) and gastroesophageal reflux disease (GERD). Likewise, both functional heartburn (FH) and IBS are functional digestive disorders that may occur in the same patients. However, data establishing a solid link between FH and IBS are lacking, mainly because the clinical definition of FH has undergone substantial changes over the years. The available literature on the overlap between GERD or FH and IBS highlights considerable heterogeneity in terms of the criteria and diagnostic procedures used to assess heartburn and IBS. In particular, several epidemiological studies included patients with concomitant IBS and GERD without any attempt to distinguish FH (as defined by the Rome III criteria) from GERD via pathophysiological investigations. Independent of these critical issues, there is preliminary evidence supporting a significant degree of FH-IBS overlap. This underscores the need for studies based on updated diagnostic criteria and accurate pathophysiological classifications, particularly to distinguish FH from GERD. This distinction would represent an essential starting point to achieving a better understanding of pathophysiology in the subclasses of patients with GERD and FH and properly assessing the different degrees of overlap between IBS and the subcategories of heartburn.The present review article intends to appraise and critically discuss current evidence supporting a possible concomitance of GERD or FH with IBS in the same patients and to highlight the pathophysiological relationships between these disorders.

Effect of age and correlation between esophageal visceral chemosensitivity and mechanosensitivity in healthy Japanese subjects

BACKGROUND

The aim of this study was to examine the impact of age on esophageal sensation, and to determine whether esophageal mechanosensitivity and chemosensitivity are correlated in healthy Japanese subjects.

METHODS

To evaluate chemosensitivity, a catheter was inserted and placed 10 cm above the upper border of the lower esophageal sphincter (LES), which was determined with an esophageal manometric catheter. After saline had been infused into the esophagus at a rate of 10 mL/min for 2 min, 0.1 N hydrochloric acid, instead of saline-without the subjects' knowledge-was infused for 10 min at the same rate. The acid perfusion sensitivity score (APSS) was assessed. To evaluate mechanosensitivity, a barostat test was performed, with a balloon being placed 10 cm above the upper border of the LES. The initial perception threshold (IPT), pain threshold (PT), and maximal pain were quantified.

RESULTS

The APSS was significantly inversely correlated with age. IPT, PT, and mean maximal pain were significantly correlated with age. Body mass index, drinking, and smoking habits were not correlated with the esophageal perception threshold. The correlation of chemosensitivity and mechanosensitivity was also assessed, and the APSS was inversely correlated with IPT, PT, and maximal pain.

CONCLUSIONS

The thresholds of esophageal visceral chemosensitivity and mechanosensitivity in same individuals were significantly correlated and both of these thresholds were inversely correlated with age.

Functional heartburn: definition and management strategies

Functional heartburn (FH) is a functional gastro-intestinal disorder characterized by symptoms of heartburn not related to gastro-esophageal reflux. The absence of evidence of reflux-related symptoms relies on absence of esophagitis at endoscopy (including biopsies to exclude eosinophilic esophagitis), a normal esophageal acid exposure during esophageal pH-monitoring together with a negative symptom-reflux association analysis and an unsatisfactory response to proton pump inhibitor therapy. Addition of impedance measurement to pH-monitoring is likely to increase the number of patients with recognized reflux-related symptoms. The pathophysiology of functional heartburn remains largely unknown but involves disturbed esophageal perception and psychological factors such as depression, anxiety and somatization. The treatment of FH remains largely empirical and an individual approach is therefore recommended. The clinician should provide reassurance and refrain from performing too many invasive tests or therapeutic procedures. The use of pain modulators is recommended by most experts despite the lack of appropriate clinical trials to support it.

Brain activity following esophageal acid infusion using positron emission tomography

AIM: To investigate symptoms and brain activity following esophageal acid infusion.

METHODS: Fifteen healthy volunteers were recruited for the study. Hydrochloric acid (pH 1 and 2) and distilled water (pH 7) were randomly and repeatedly infused into the esophagus. The brain activity was evaluated by positron emission tomography. The severity of heartburn elicited by the infusion was rated on an auditory analog scale of 0-10.

RESULTS: The severity of heartburn following each infusion showed a step-wise increase with increasing acidity of the perfusate. The heartburn scores were significantly higher in the second pH 1 infusion compared with the first infusion. Acid and distilled water infusion induced activation of various brain areas such as the anterior insula, temporal gyrus, and anterior/posterior cingulate cortex. At pH 1 or 2, in particular, activation was observed in some emotion-related brain areas such as the more anterior part of the anterior cingulate cortex, parahippocampal gyrus, or the temporal pole. Strong activation of the orbitofrontal cortex was found by subtraction analysis of the two second pH 1 infusions, with a significant increase of heartburn symptoms.

CONCLUSION: Emotion-related brain areas were activated by esophageal acid stimulation. The orbitofrontal area might be involved in symptom processing, with esophageal sensitization induced by repeated acid stimulation.

Quantitative assessment and characterization of visceral hyperalgesia evoked by esophageal balloon distention and acid perfusion in patients with functional heartburn, nonerosive reflux disease, and erosive esophagitis

BACKGROUND AND OBJECTIVES

The role of esophageal hypersensitivity in functional heartburn (FH) with negative pH test, negative symptom index, and the proton pump inhibitor (PPI) failure has not been established. The aim of this study was to investigate the characterization of visceral hyperalgesia evoked by esophageal balloon distention and acid perfusion in patients with FH, nonerosive reflux disease, and erosive esophagitis and further characterize the pathophysiologic mechanism of FH.

METHODS

A total of 21 FH patients (with esophageal acid exposure <3.1% and a symptom index<50% and nonresponse to a therapeutic trial with proton pump inhibitors, 25 Nonerosive reflux disease (NERD) patients (with esophageal acid exposure>4%), 23 erosive esophagitis (EE) patients (LA grade B to D), and 18 healthy controls were recruited in the study. Mechanosensitivity including the initial perception threshold (IPT) and pain threshold (PT) was evaluated by using a Barostat with a double-random staircase distension protocol. Chemosensitivity was graded along a visual analog scale after perfusion of saline and 0.1 N HCl.

RESULTS

The baseline IPTs and PTs were all lower in patients with FH, NERD, and EE than in the controls (all P<0.01). In addition, the baseline PT in FH patients was significantly lower than those in NERD (P=0.015) and EE patients (P<0.001). After acid perfusion, the mean symptom intensity scores were significantly greater in patients with FH, NERD, and EE than those in the controls (all P<0.001). The postacid perfusion IPTs in patients with FH, NERD, and EE were all significantly lower than the corresponding baseline values (all P<0.01). The PTs in FH (P=0.026) and EE patients (P<0.001) were significantly lower than the corresponding baseline values. Moreover, the postacid perfusion PT was significantly lower in FH patients than in NERD patients (P<0.001).

CONCLUSIONS

FH patients are more sensitive to mechanical or chemical stimuli than NERD patients. Sensitization of esophageal acid-sensitive chemoreceptors may exert a significant influence on the pressure-sensitive mechanoreceptors, and there is the cooperative interaction in the process of esophageal visceral hyperalgesia.

Effect of esophageal acid exposure on the cortical swallowing network in healthy human subjects

Recent studies have demonstrated common cortical activity regions associated with esophageal acidification and swallowing. The effect of sensory signals imparted on these regions by esophageal acidification on swallow-related brain activity has physiological and clinical ramifications. Our aim in this study was to determine the effect of prior, unperceived esophageal acid exposure on cortical activity associated with swallowing. Functional magnetic resonance imaging (fMRI) techniques monitored brain activity associated with volitional swallowing before and after subliminal esophageal acid stimulation. Studies were carried out in two phases. In phase I (15 healthy, right-handed subjects, age 21-49 yr, 7 female) using whole brain imaging, we documented the potentiating effects of esophageal acidification alone on swallow-related cortical activity. In phase II (10 healthy, right-handed subjects, age 20-54 yr, 5 female) using high-resolution fMRI, we measured swallow-induced regional brain activity within the cortical swallowing network before and after esophageal acidification. Unlike the phase I studies, we also tested the effect of saline perfusion alone on the cortical swallowing network in the phase II studies. Because of constraints imposed by high-resolution MRI for region-of-interest (ROI) analysis, we studied only the left hemisphere in this phase. None of the subjects developed heartburn during acid perfusion. In phase I, the number of swallow-induced activated voxels increased by 43% following esophageal acid stimulation (preacid, 44 +/- 3 voxels; postacid, 63 +/- 6 voxels; means +/- SE, P < 0.05) In phase II, contrary to saline perfusion, ROI analysis showed significantly increased regional swallow-related fMRI activity volumes as well as percent maximum signal change after esophageal acid perfusion in cingulate, prefrontal, insula, and sensory/motor regions (P < 0.05). The precuneus showed no significant change. We concluded that subliminal esophageal acid stimulation has a potentiating effect on the cortical swallowing network in healthy individuals.

Functional heartburn: what it is and how to treat it

Functional heartburn is considered one of the most common functional esophageal disorders. The disorder is more common in young women and is associated with other functional bowel disorders and psychological co-morbidity, primarily somatization. The etiology of functional heartburn remains unknown. Most patients, however, demonstrate esophageal hypersensitivity. Functional heartburn has been identified as the main cause for proton pump inhibitor (PPI) failure in patients with heartburn. Treatment is still a challenge, and patients should be started with PPI treatment. In non-responders, escalation of the PPI dose could be attempted and, if unsuccessful, pain modulators should be prescribed.

Oesophageal afferent pathway sensitivity in non-erosive reflux disease

Patients with non-erosive reflux disease (NERD) report symptoms which commonly fail to improve on conventional antireflux therapies. Oesophageal visceral hyperalgaesia may contribute to symptom generation in NERD and we explore this hypothesis using oesophageal evoked potentials. Fifteen endoscopically confirmed NERD patients (four female, 29-56 years) plus 15 matched healthy volunteers (four female, 23-56 years) were studied. All patients had oesophageal manometry/24-h pH monitoring and all subjects underwent evoked potential and sensory testing, using electrical stimulation of the distal oesophagus. Cumulatively, NERD patients had higher sensory thresholds and increased evoked potential latencies when compared to controls (P = 0.01). In NERD patients, there was a correlation between pain threshold and acid exposure as determined by DeMeester score (r = 0.63, P = 0.02), with increased oesophageal sensitivity being associated with lower DeMeester score. Reflux negative patients had lower pain thresholds when compared to both reflux positive patients and controls. Evoked potentials were normal in reflux negative patients but significantly delayed in the reflux positive group (P = 0.01). We demonstrate that NERD patients form a continuum of oesophageal afferent sensitivity with a correlation between the degree of acid exposure and oesophageal pain thresholds. We provide objective evidence that increased oesophageal pain sensitivity in reflux negative NERD is associated with heightened afferent sensitivity as normal latency evoked potential responses could be elicited with reduced afferent input. Increased oesophageal afferent pain sensitivity may play an important role in a subset of NERD and could offer an alternate therapeutic target.

Functional heartburn, nonerosive reflux disease, and reflux esophagitis are all distinct conditions—A debate: Pro

Gastroesophageal reflux disease (GERD) traditionally has been approached as a spectrum-continuum, suggesting that patients may progress over time and develop a more severe esophageal mucosal involvement. The spectrum-continuum conceptual model had a profound impact on the research priorities in GERD, as well as on proposed diagnostic algorithms and therapeutic strategies. Natural course studies in GERD are almost always retrospective and commonly afflicted with a plethora of shortcomings. Factors that affect quality of natural course studies in GERD include the following: index endoscopy results are taken at face value; antireflux treatment is consumed until index endoscopy and/or offered during the follow-up phase; pathophysiologic, anatomic, and genetic factors are overlooked; and lack of confirmation of the durability of the new esophageal mucosal finding. Functional heartburn is common and likely to affect a large subset of patients presenting with heartburn. Evidence to support progression of functional heartburn to nonerosive reflux disease (NERD), erosive esophagitis, or Barrett's esophagus is very scarce. The largest population-based or longest-duration natural course studies report that only 10% of patients progress from NERD to erosive esophagitis over time. The other GERD patients remained within their respective phenotypic presentations of GERD.

Review article: the pathophysiology of gastro-oesophageal reflux disease

BACKGROUND

Gastro-oesophageal reflux disease (GERD) is a common condition that develops when the reflux of stomach contents causes troublesome symptoms and/or complications.

AIM

To review the current knowledge on the underlying factors contributing to GERD, with particular emphasis on the most recent research.

METHODS

Literature searches were conducted in Medline and EMBASE. The abstracts from recent large congresses were also reviewed to ensure coverage of the latest findings.

RESULTS

The pathophysiological factors causing GERD can be split into those inducing greater exposure of the oesophagus to stomach contents, and those that provide increased perception of reflux or increased mucosal damage. Transient lower oesophageal sphincter relaxations, which are likely to be triggered by gastric distension, appear to be a key physiological cause of GERD. Excessive reflux may also be provoked by impaired oesophageal or gastric clearance mechanisms. Pre-epithelial, epithelial and post-epithelial defences all normally protect the oesophagus from injury, and may be compromised in individuals with GERD. Heartburn could also be caused by oesophageal hypersensitivity as a result of visceral neural pathway dysfunction.

CONCLUSION

The pathophysiology of GERD is multifactorial, and abnormalities in the gastro-oesophageal junction, the stomach, the oesophagus and the nervous system may all contribute to this disease state.