What Causes the Stomach to Push Up into the Esophagus
A hiatal hernia occurs when the stomach pushes up through the diaphragmatic opening (hiatus) into the chest, primarily due to weakening of the phrenoesophageal membrane and widening of the esophageal hiatus, with the most common type being a sliding hiatal hernia where the gastric cardia and gastroesophageal junction migrate above the diaphragm. 1
Types of Hiatal Hernias
The stomach can herniate through the diaphragm in four distinct patterns:
- Type I (Sliding Hiatal Hernia) - accounts for 90% of cases, where the esophageal hiatus widens and allows the gastric cardia and gastroesophageal junction to slide upward above the diaphragm 1
- Type II (Paraesophageal Hernia) - represents 10% of cases, where a defect in the phrenoesophageal membrane allows the gastric fundus to herniate while the gastroesophageal junction stays in normal position 1
- Type III - combines features of both Type I and II, with both fundus herniation and displacement of the gastroesophageal junction 1
- Type IV - a large diaphragmatic hernia that can accommodate additional organs including colon and spleen 1
Primary Mechanisms Causing Herniation
Anatomical Defects
The fundamental problem is defects in the phrenoesophageal membrane, which is the connective tissue that anchors the esophagus to the diaphragm 1. When this membrane weakens or tears, it creates an opening for the stomach to migrate upward.
Contributing Factors
Several factors increase the likelihood of hiatal hernia development:
- Increased age - hiatal hernias become progressively more common with aging, similar to the age-related increase in reflux disease 2
- Obesity - excess weight increases intra-abdominal pressure, which can force the stomach upward through a weakened hiatus 2
- Increased intra-abdominal pressure from chronic straining, heavy lifting, or persistent coughing can progressively widen the hiatus 3
How Hiatal Hernia Disrupts Normal Anatomy
Once the stomach herniates, it creates a cascade of anatomical and physiological problems:
- Reduces lower esophageal sphincter (LES) length and pressure, compromising the primary barrier against reflux 4
- Impairs the diaphragmatic crural function, which normally acts as a "second sphincter" during abrupt increases in abdominal pressure 2
- Creates a reservoir effect where the herniated portion of stomach acts as a sac that allows reflux back into the esophagus during swallowing 4
- Increases the cross-sectional area of the esophagogastric junction, making it easier for gastric contents to reflux 4
Clinical Significance
Hiatal hernia is not just an incidental finding but a major pathophysiological contributor to gastroesophageal reflux disease (GERD), particularly in severe cases 4. The presence of hiatal hernia is found in 50% to 94% of patients with GERD 5.
Impact on Reflux Mechanisms
Patients with hiatal hernia experience more reflux through mechanisms beyond the typical transient LES relaxations:
- Reflux during low LES pressure periods - the hernia allows reflux even when the sphincter hasn't actively relaxed 3
- Reflux during normal swallow-associated LES relaxations - swallowing that wouldn't cause reflux in normal anatomy now permits gastric contents to enter the esophagus 3
- Reflux during straining and deep inspiration - activities that increase abdominal pressure overcome the weakened barrier 3
Progressive Nature
Hiatal hernia should be viewed as a continuum rather than an all-or-none phenomenon, with larger hernias having greater pathophysiological significance 5. The size of the hernia correlates with severity of reflux and complications including Barrett's esophagus and esophageal adenocarcinoma 6, 4.
Diagnostic Considerations
When hiatal hernia is suspected, fluoroscopy such as biphasic esophagram or upper GI series is the most useful diagnostic test for confirming the diagnosis and determining hernia size 7.
Important Clinical Pitfall
While hiatal hernia commonly causes reflux symptoms, tachycardia associated with hiatal hernia should raise concern for strangulated hernia, a surgical emergency that typically presents with fever, continuous abdominal pain, and signs of systemic inflammatory response 7. This requires immediate surgical evaluation rather than routine GERD management.