The esophageal hiatus is a normal opening within the diaphragm, the large muscle separating the chest from the abdominal cavity. This passageway allows the esophagus to pass through the diaphragm and connect with the stomach. The hiatus is an elliptical opening formed by the muscular fibers of the diaphragm itself. It is located where the thoracic and abdominal cavities meet, making it a point of transition for the digestive tract.
Anatomical Function
The esophageal hiatus is an active component of the body’s anti-reflux barrier, a system that prevents stomach contents from flowing back into the esophagus. The hiatus is formed by the crural diaphragm, which wraps around the esophagus to provide external compression. This compression supports the lower esophageal sphincter (LES), a ring of muscle at the bottom of the esophagus that stays contracted to keep the junction closed.
This dual-sphincter mechanism, involving the internal LES and external pressure from the crural diaphragm, creates a high-pressure zone. This pressure resists upward force from the abdomen during moments of increased intra-abdominal pressure like coughing or straining. The phrenoesophageal ligament, a flexible membrane, anchors the esophagus to the diaphragm, allowing for movement during swallowing while helping to maintain this barrier.
The Hiatal Hernia
A hiatal hernia occurs when the upper part of the stomach pushes through the esophageal hiatus and into the chest cavity. This happens when the diaphragm muscle around the hiatus weakens, allowing the stomach to bulge through the opening. This weakening can be caused by age-related changes, injury, or persistent pressure on the surrounding muscles from chronic coughing, heavy lifting, or straining.
The most common type is a sliding hiatal hernia, which accounts for about 95% of cases. In this form, the junction where the esophagus meets the stomach, along with a portion of the stomach, slides up into the chest. A less common type is the paraesophageal hernia, where part of the stomach herniates into the chest alongside the esophagus, while the gastroesophageal junction remains in its normal position. Obesity and pregnancy can also contribute by increasing pressure within the abdomen.
Symptoms of a Weakened Hiatus
Many small hiatal hernias do not produce noticeable symptoms. When symptoms occur, they are often the result of gastroesophageal reflux disease (GERD). The hernia compromises the anti-reflux barrier, allowing stomach acid into the esophagus, which leads to the most common symptom: heartburn. This is a burning sensation in the chest that can worsen after eating or when lying down.
Other symptoms include regurgitation, the sensation of acid or food coming back into the throat or mouth. Some individuals experience dysphagia, or difficulty swallowing, if the hernia compresses the esophagus. Non-cardiac chest pain is also possible and can be mistaken for a heart-related issue. In some cases, a large hernia can press against the lungs, causing shortness of breath.