Gastroesophageal Reflux

Gastroesophageal reflux is the movement of gastric contents back up into the esophagus. It becomes gastroesophageal reflux disease (GERD) when reflux causes troublesome symptoms, such as heartburn and regurgitation, or leads to mucosal injury. Reflux is a normal physiological event in small amounts; it is the frequency, volume, and consequences of reflux that distinguish disease from physiology.

Definition

Gastroesophageal reflux disease is a condition that develops when the reflux of stomach contents into the esophagus causes troublesome symptoms or complications, as set out in the Montreal global consensus definition.

Scope

This topic covers the mechanisms of reflux, the consensus definition that separates physiological reflux from GERD, the objective measurement of esophageal acid exposure, and the spectrum of presentations and complications. It frames how reflux disease is defined and characterised for reference and education; it is not a treatment guide and contains no individualised management advice.

Core questions

• What mechanisms allow gastric contents to reflux into the esophagus?
• When does physiological reflux become gastroesophageal reflux disease?
• How is esophageal acid exposure measured and interpreted objectively?

Key concepts

• Transient lower esophageal sphincter relaxations
• Esophageal acid exposure time
• Montreal definition of GERD
• Erosive versus non-erosive reflux disease
• Esophagogastric junction and hiatal hernia
• pH-impedance monitoring and the Lyon Consensus thresholds

Mechanisms

Reflux occurs when the antireflux barrier at the esophagogastric junction fails to contain gastric contents. The dominant mechanism is transient lower esophageal sphincter relaxation — brief relaxations unrelated to swallowing — supplemented by a hypotensive sphincter, impaired esophageal clearance, and anatomical disruption such as hiatal hernia. The refluxate, which may be acidic or weakly acidic, contacts the esophageal mucosa and, when exposure is prolonged, produces symptoms and inflammation. Objective assessment quantifies acid exposure time by ambulatory pH or pH-impedance monitoring; the Lyon Consensus defines thresholds that distinguish conclusive evidence of pathological reflux from normal exposure, and the Montreal consensus framed the symptom- and complication-based definition of the disease.

Clinical relevance

GERD is one of the most common conditions seen in primary care and gastroenterology, and its presentations range from typical heartburn and regurgitation to esophageal complications and possible extra-esophageal symptoms. This entry describes how the disease is defined, measured, and classified for reference and education; it does not provide diagnostic algorithms or treatment recommendations for any individual.

Epidemiology

Systematic reviews report that GERD symptoms are common across populations, with prevalence estimates that vary by region and by how the disease is defined, and evidence of a rising trend over recent decades. The variability underscores why consensus definitions and objective measurement are emphasised when comparing studies.

History

The conception of reflux disease shifted from an erosion-centred, endoscopic view toward a symptom- and consequence-based definition codified by the 2006 Montreal consensus, which formally separated GERD from physiological reflux. Diagnosis evolved in parallel from acid-only pH monitoring to combined pH-impedance testing, and the 2018 Lyon Consensus established thresholds for what constitutes conclusive evidence of pathological reflux.

Debates

How should non-erosive reflux disease and reflux hypersensitivity be classified?

A large share of patients with reflux symptoms have no visible mucosal erosions, and distinguishing true non-erosive reflux disease from reflux hypersensitivity and functional heartburn depends on objective reflux metrics and symptom-reflux association, an area the Lyon Consensus addresses but where boundaries remain debated.

Key figures

• Nimish Vakil
• C. Prakash Gyawali
• Peter J. Kahrilas
• Hashem B. El-Serag

Seminal works

• vakil-2006-montreal
• gyawali-2018-lyon
• katz-2022-acg

Frequently asked questions

What is the difference between reflux and GERD?

Reflux of small amounts of stomach contents is a normal event; gastroesophageal reflux disease is diagnosed when that reflux causes troublesome symptoms or complications, as defined by the Montreal consensus.

What mainly causes acid to reflux into the esophagus?

The leading mechanism is transient relaxation of the lower esophageal sphincter, often combined with a weak sphincter, impaired esophageal clearance, or a hiatal hernia that disrupts the antireflux barrier.