Gastroesophageal Reflux Disease I: Meaning and Pathophysiology

Gastroesophageal reflux disease (GERD) is a chronic condition where stomach contents, including acidic gastric juices and bile, frequently flow back into the esophagus, causing irritation and inflammation. Rather than a single disease, GERD is a syndrome encompassing various symptoms and complications. Approximately 15 million Americans experience GERD symptoms, making it the most prevalent upper gastrointestinal problem.

The lower esophageal sphincter (LES) normally prevents backward flow of stomach contents by acting as a barrier. When the LES becomes incompetent, it fails to maintain this seal, allowing gastric contents to reflux into the esophagus, especially when lying down or during increased intra-abdominal pressure. This incompetent LES is the chief factor contributing to GERD development.

A hiatal hernia occurs when part of the stomach protrudes through the diaphragm into the chest, displacing the stomach upward and breaching the normal abdominal-chest boundary. This anatomical anomaly compromises the integrity of the lower esophageal sphincter, allowing stomach acid to flow freely back into the esophagus, causing heartburn and regurgitation symptoms.

Tobacco use, including smoking and smokeless products, worsens GERD through multiple mechanisms. Smoking relaxes the lower esophageal sphincter, allowing stomach contents to reflux more easily. Additionally, tobacco increases stomach acid production, reduces saliva production that normally neutralizes acid, and impairs esophageal motility, all exacerbating GERD symptoms.

Obesity increases GERD risk by raising intra-abdominal pressure in overweight individuals. This elevated pressure promotes transient lower esophageal sphincter relaxations and gastric distension, particularly after meals. The increased pressure forces stomach contents upward, overwhelming the esophagus's defensive mechanisms and triggering reflux symptoms.

When the lower esophageal sphincter fails, hydrochloric acid, bile, pepsin, and pancreatic enzymes reflux into the esophagus, causing mucosal injury and esophagitis. The degree of inflammation depends on the volume and composition of refluxed gastric contents and the protective capabilities of the esophageal lining. These substances overwhelm the esophagus's natural defensive mechanisms.

Certain medications, particularly nonsteroidal anti-inflammatory drugs (NSAIDs), reduce lower esophageal sphincter pressure and exacerbate GERD. Fatty foods similarly decrease LES pressure. Alcohol consumption and smoking also contribute to symptom development. These substances either relax the sphincter or increase stomach acid production, promoting reflux into the esophagus.