Etiology

• This condition is likely to have a complex, multifactorial etiology and pathophysiology involving a number of interrelated factors including displacement of the gastro-esophageal sphincter, changes in the angle of insertion of the esophagus into the stomach, anatomical changes to the hiatal canal and phrenico-esophageal ligament, esophageal motility disorders, underlying respiratory, neurological or neuromuscular disease. Upper respiratory obstruction may exacerbate the clinical signs associated with hiatal hernia. Hiatal hernia has also been reported following surgical correction of chronic diaphragmatic hernia Diaphragm: repair of diaphragmatic defects.
• Congenital cases have been proposed to result from congenital weakening or incomplete development of phrenico-esophageal ligament.
• Trauma (in acquired cases).

Specific

• Prior trauma.

Pathophysiology

• Phrenico-esophageal ligament around esophageal hiatus is congenitally weakened or incomplete, allowing abdominal organs to move into thoracic cavity.
• Abdominal esophagus and stomach are most frequently herniated.
• Classified according to position of gastro-esophageal sphincter (GOS):
  • Axial: GOS found cranial to esophageal hiatus, many are "sliding", ie the abdominal esophagus +/- part of stomach herniate intermittently. This is the commonest type of hiatal hernia.
  • Para-esophageal: GOS occupies a normal position while fundus/other abdominal viscus herniates through phrenico-esophageal ligament.
  • Combined: both GOS and other abdominal organs lie cranial to the hiatus.

• When GOS moves through the hiatus into thorax, thoracic pressure (being lower than intra-abdominal pressure) allows gastro-esophageal reflux → esophagitis Esophagitis.
• Esophagitis further decreases the gastro-esophageal pressure resulting in further tendency for gastro-esophageal reflux.
• Esophageal irritation or GOS obstruction results in hypersalivation, vomiting or regurgitation.
• Abnormal/reduced esophageal motility and mega-esophagus may be present in some cases. This may be primary or secondary to the hiatal hernia.
• Weight loss or cachexia follows in severe cases.
• Aspiration pneumonia follows persistent vomiting/regurgitation.
• Herniation of duodenum can occur with resulting obstruction of the common bile duct and jaundice has been recorded but is rare.
• Increased inspiratory effort may cause an increase in negative intra-esophageal and intrapleural pressure so that the abdominal esophagus and part of the stomach are "pulled" into the thorax by the increased pressure differential between intra-abdominal and intrapleural pressure.
• The presence of acid in the lower esophagus can cause laryngo- and bronchospasm which further worsen the respiratory signs.