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Alterations confined to the gastro-oesophageal junction: the relationship between low LOSP, TLOSRs, hiatus hernia and acid pocket

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The gastro-oesophageal junction is a specialised segment of the gut designed to prevent reflux of gastric contents into the oesophagus. This task is fulfilled by two structures, i.e. the lower oesophageal sphincter and the crural diaphragm, which generate a high pressure zone. Especially during low pressure at the junction, as in case of long-lasting transient lower oesophageal sphincter relaxations, reflux can occur but mainly if a positive pressure gradient exists between stomach and the oesphagogastric junction. Although patients with gastro-oesophageal reflux disease have increased oesophageal acid exposure compared to controls, the number of transient relaxations is not increased compared to healthy controls. Instead, the risk to have acid reflux is at least doubled in patients, especially in those with a hiatal hernia, most likely as a result of the supradiaphragmatic position of the acid pocket. In hiatal hernia patients, the acid pocket is indeed often trapped in the hernia above the diaphragm. Which factors exactly determine the physical composition (liquid or gas) and the proximal extent of the refluxate however requires further research.

Introduction

The junction between the oesophagus and the stomach is a specialised region, composed of the lower oesophageal sphincter (LOS) and its adjacent anatomic structures, the gastric sling and the crural diaphragm. [1] The main physiological task of the oesophago-gastric junction (OGJ) is to prevent reflux of gastric contents into the oesophagus while at the same time passage of ingested food into the stomach must be guaranteed. Somewhat related to the latter, the high pressure zone should also allow retrograde passage of gastric contents into the oesophagus during belching or vomiting. This complicated task is achieved by a high pressure zone which keeps the junction between the oesophagus and the stomach continuously closed, but which is still able to relax briefly via input from inhibitory neurons to permit passage through the sphincter. [2]

Section snippets

High pressure zone at the oesophago-gastric junction

Important to emphasise is that the OGJ is located at the interface between two cavities, the thoracic and abdominal cavity, both with a very different pressure profile. Intra-abdominal pressure is not only higher than intra-thoracic pressure, it is also differentially influenced by respiration: inspiration decreases intra-thoracic (intra-oesophageal) pressure whereas it increases intra-abdominal (intragastric) pressure. This pressure gradient between the intra-abdominal stomach and

Relaxation of the lower oesophageal sphincter

As a gatekeeper between stomach and oesophagus, the OGJ not only has to prevent reflux of gastric contents, it also has to regulate and allow flow of ingested food towards the stomach (swallow-induced relaxation), or even allow excess of air trapped in the stomach to escape (belching, transient lower oesophageal sphincter relaxations or TLOSRs).

Swallow-induced relaxation is part of primary peristalsis, a complex reflex generated by the swallowing program generator in the swallowing centre in

Gastro-oesophageal reflux

Reflux of gastric contents into the oesophagus is a physiological phenomenon also occurring in healthy individuals. In patients with gastro-oesophageal reflux disease however, the frequency of reflux is increased or it is abnormally perceived with mucosal damage and symptoms such as regurgitation and heartburn.

With increasing interest in the mechanisms underlying gastro-oesophageal reflux, it is becoming clear that several conditions should be fulfilled before the gatekeeper really fails and

Summary

During the past 2 to 3 decades, our understanding of the mechanisms has tremendously increased, largely due to the introduction of new methodologies. Sleeve manometry has contributed significantly to the identification of TLOSRs as a main reflux mechanism and has led to the development of reflux inhibitors, a new class of drugs targeting TLOSRs, as potential treatment for GORD. Similarly, since the introduction of impedance recording, non-acidic reflux is increasingly recognised to contribute

Acknowledgements

GEB is supported by a grant (Odysseus program, G.0905.07) of the Flemish “Fonds Wetenschappelijk Onderzoek” (FWO).

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