Gastric luminal contents and gas–liquid interface at the gastro-esophageal junction (GEJ interface)

The gastric luminal contents and the gas–liquid interface at the gastro-esophageal junction (GEJ) represent a physiological and physical environment rather than a specific molecular receptor or enzyme. This site is the primary location of the "acid pocket," a phenomenon where a layer of unbuffered, highly acidic gastric juice (pH ~1.5) sits on top of the ingested meal postprandially [PMID: 23510145]. Because this pocket is positioned near the GEJ, it serves as the main reservoir for acid reflux into the esophagus, particularly in patients with hiatal hernias or weak lower esophageal sphincters [PMID: 11069577]. Therapeutic intervention at this interface is achieved through raft-forming agents, most notably alginates. Upon contact with gastric acid, alginates precipitate into a low-density, pH-neutral gel (a "raft") that incorporates carbon dioxide bubbles, allowing it to float specifically at the gas–liquid interface [PMID: 22222325]. This raft acts as a physical barrier that prevents the reflux of acid, pepsin, and bile into the esophagus, or is refluxed itself in place of the acidic contents [PMID: 24630392]. Unlike systemic medications like proton pump inhibitors that alter gastric pH globally, targeting this interface provides a localized, mechanical solution to the symptoms of gastroesophageal reflux disease (GERD).

Other names

Acid pocketPostprandial acid pocketGastric gas–liquid interfaceGEJ acid reservoir

Formation of a physical pH-neutral raft that floats on the gastric contents to mechanically block reflux.