A New Frontier in GERD: The Gastric Pocket

Researchers examined the effects of proton pump inhibitors on the highly acidic pocket of gastric juice at the esophagogastric junction.

The gastric acid pocket is an area of unbuffered, highly acidic gastric juice that forms at the esophagogastric junction after meals. It floats between 2 less acidic layers of stomach juices. Experts describe it as the reservoir from which acid reflux events originate. The gastric pocket was only identified in 2001, so researchers still have many questions about its function and effects.

Since little is known about how the acid pocket’s position, size, and acidity affect therapeutic effects of proton pump inhibitors (PPIs) in patients with gastroesophageal reflux disease (GERD) and vice versa, this is an area of interest. A team of researchers has published a study examining this issue in the May 2014 issue of Clinical Gastroenterology and Hepatology.

The researchers enrolled 36 GERD patients in this study designed to look at how the gastric pocket interacts with PPIs. Among the study participants, half were not taking PPIs and the remainder were taking various PPIs. The researchers analyzed each participant’s stomach using high-resolution manometry and pH-impedance monitoring after a standardized meal. They also used scintigraphy after intravenous administration of ^99mtechnetium-pertechnetate to visualize the acid pocket. Ultimately, they aspirated the acid pocket to measure its pH level.

Patients who took PPIs had significantly fewer acid reflux episodes than those who did not. PPI-treated patients had smaller acid pockets that were more often located below the diaphragm. The mean pH of the acid pocket was significantly higher in PPI-treated patients not taking PPIs and its pH was similar to the pH measured in patients’ refluxate.

From their observation, the researchers concluded:

• PPI treatment causes gastric secretions to accumulate on top of ingested food and form a pocket.
• PPIs increase the pH of refluxate, and if the acid pocket’s pH is higher (less acidic), the refluxate’s pH is also.
• PPI treatment reduces the size of the acid pocket, explaining why the acid pocket is located below the diaphragm more often during the use of PPIs.

They conclude that the acid pocket appears to be a reservoir from which reflux occurs during treatment with PPIs. PPIs might affect the size, acidity, or position of the acid pocket, which contributes to their efficacy in patients with GERD. The acid pocket may be the source of refractory symptoms.

Ms. Wick is a visiting professor at the University of Connecticut School of Pharmacy and a freelance writer from Virginia.