Digestive Diseases Center, Showa University Koto Toyosu Hospital

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EPSIS (Endoscopic pressure study integrated system)

What is GERD?

  • Gastroesophageal reflux disease (GERD) is a growing health problem with an estimated prevalence of 20% in the US population and an increasing incidence worldwide.
  • Acid reflux happens when contents from your stomach move up into your esophagus. It is also called acid regurgitation or gastroesophageal reflux.
  • If you have symptoms of acid reflux more than twice a week, you might have a condition known as gastroesophageal reflux disease (GERD)

What are the causes of GERD?

  • The lower esophageal sphincter (LES) plays a key role in these reflux phenomen (LES is a circular band of muscle at the end of your esophagus). Acid reflux happens when your LES does not tighten or close properly. This allows digestive juices and other contents from your stomach to rise into your esophagus.

How is GERD diagnosed?

Esophageal 24hour pH testing

Esophageal 24hour pH testing is the gold standard in diagnosing GERD. A thin catheter is placed in the esophagus through nostril to identify when, and for how long, stomach acid regurgitates. This test is done in one-day admission to the hospital.

EPSIS (Endoscopic pressure study integrated system)

  • Endoscopic pressure study integrated system (EPSIS) has been developed at our center to assess the function of lower esophageal sphincter (LES).
  • EPSIS allows to monitor an intragastric pressure (Pressure inside the stomach) while inflating the stomach during gastroscopy. Endoscopic evaluation of air valve mechanism of LES function can be achieved.

Figure a: If the stomach hold enough air (Uphill pattern of intragastric pressure), it means that LES valve is working properly ➡ High possibility that there is no acid reflux

Figure b: If the stomach can’t hold enough air (Flat pattern of intragastric pressure), it means that LES valve is impaired ➡ High possibility of acid reflux

  • This study only takes approximately 5 minutes during gastroscopy and is considered very safe with minimal discomfort. No adverse events have been experienced. EPSIS can be used as an ancillary diagnostic tool to diagnose acid reflux.


  • Can be easily and safely performed during endoscopy. This will be done under sedation with no discomfort.
  • No need to be admitted to the hospital unlike 24pH monitoring.

How does it work?

  1. Routine endoscopy is performed to see if there is any obvious sign of acid reflux e.g. erosive esophagitis (inflammation in the esophagus) and Barrett’s esophagus (Chronic sign of acid reflux, known to be precursor of esophageal cancer).
  2. After through observation in the esophagus, stomach, and duodenum, CO2 is continuously insufflated. This insufflation is continued till the air evacuates (burping). While insufflating, intragastric pressure (pressure in the stomach) is being recorded.
  3. We assess the at which point the air evaluates and how well stomach holds air inside. This is equal to checking the function of LES (valve between esophagus and stomach).

Please feel free to contact us if you have any symptoms of GERD.


  1. Inoue H, Shimamura Y, Rodriguez de Santiago E et al. Diagnostic performance of the endoscopic pressure study integrated system (EPSIS): a novel diagnostic tool for gastroesophageal reflux disease. Endoscopy 2019; 51: 759-762
  2. Iwaya Y, Inoue H, Rodríguez de Santiago E et al. Endoscopic pressure study integrated system reflects gastroesophageal junction competence in patients with erosive esophagitis and Barrett´s esophagus. Dig Endosc 2020, DOI: 10.1111/den.13644: