What causes a hiatal hernia?

Causes of Hiatal Hernia

Hiatal hernias primarily occur due to widening of the esophageal hiatus, allowing displacement of the gastroesophageal junction and stomach into the thoracic cavity. 1

Types and Classification

Hiatal hernias are categorized as acquired diaphragmatic hernias (ADH) and can be classified into four main types:

• Type I (Sliding Hiatal Hernia): Most common type (90%) where the esophageal hiatus widens, allowing herniation of the gastric cardia and migration of the gastroesophageal junction above the diaphragm 1
• Type II (Paraesophageal Hiatal Hernia): Accounts for 10% of hiatal hernias, involving a defect in the phrenoesophageal membrane that allows herniation of the gastric fundus while the gastroesophageal junction remains in normal position 1
• Type III: Combination of Type I and II, with both herniation of gastric fundus and displacement of the gastroesophageal junction 1
• Type IV: Large diaphragmatic hernia that can accommodate herniation of additional viscera including stomach, colon, and spleen 1

Primary Causative Factors

Anatomical Factors

• Widened Esophageal Hiatus: The fundamental anatomical defect allowing abdominal contents to protrude into the thoracic cavity 2
• Weakened Diaphragmatic Muscle: Deterioration of diaphragmatic muscle integrity contributes to hiatal hernia development 3
• Defects in Phrenoesophageal Membrane: Particularly important in paraesophageal hernias (Type II) 1

Risk Factors and Contributing Conditions

• Age-Related Changes: Hiatal hernias become more common with advancing age due to weakening of supporting tissues 4
• Obesity: Significant risk factor that increases intra-abdominal pressure and strain on the diaphragmatic hiatus 5, 6
• Increased Intra-abdominal Pressure: Chronic conditions that increase pressure within the abdominal cavity contribute to hiatal hernia development 5
• Gender: Males with hiatal hernias have a higher association with inguinal hernias (2.86 times more likely), suggesting a possible common etiology related to abdominal wall weakness 5

Pathophysiological Mechanisms

• "Push" Factors: Excessive pressure from the abdominal cavity pushing contents through the diaphragm, supported by the 2.5-fold increased risk of inguinal hernia in patients with hiatal hernia 5
• Anatomical Disruption: Widening of the esophageal hiatus allows displacement of the gastroesophageal junction above the diaphragm 1, 2
• Tissue Deterioration: Progressive weakening of the supporting structures around the gastroesophageal junction 3

Clinical Significance

• Size Matters: Hiatal hernias ≥2 cm are associated with significantly worse gastroesophageal reflux parameters compared to smaller hernias 6
• Functional Impairment: Large, non-reducing hernias impair esophageal emptying and prolong acid clearance time, especially in the supine position 4
• Diaphragmatic Function: The crural diaphragm normally serves as a "second sphincter" during increases in intra-abdominal pressure, a function impaired in individuals with gaping hiatus 4

Common Pitfalls in Understanding Hiatal Hernias

• Not All Hiatal Hernias Are the Same: The specific type and size significantly impact clinical manifestations and treatment approaches 6
• Asymptomatic vs. Symptomatic: Many hiatal hernias may be asymptomatic, with clinical significance determined by size and associated functional impairment 3, 6
• Relationship to GERD: While hiatal hernias are associated with gastroesophageal reflux disease, they may not always be the initiating factor but can act as a sustaining factor accounting for disease chronicity 4