A hiatal hernia occurs when part of the stomach pushes upward through the diaphragm. The opening in the diaphragm is called the hiatus. Normally, the oesophagus passes through this opening to reach the stomach.
Doctors classify hiatal hernias into four main types. Type I is the most common form. In this type, the stomach and the gastroesophageal junction slide upward together. Doctors therefore call it a sliding hiatal hernia.
Type II is known as a paraesophageal hernia. Here, the stomach moves up beside the oesophagus while the junction stays in place. Type III combines features of both Type I and Type II. Type IV involves other abdominal organs that also enter the chest cavity.
The pathophysiology begins with weakness in the diaphragmatic muscles. Increased pressure inside the abdomen can force the stomach upward. Factors such as ageing, obesity, and chronic coughing raise this pressure. As a result, the normal barrier between the stomach and the chest weakens.
This anatomical change often disrupts the lower oesophageal sphincter. The sphincter normally prevents stomach acid from flowing back. When it fails, acid reaches the oesophagus easily.
Hiatal hernia shows a strong association with gastroesophageal reflux disease, or GERD. Many patients with a sliding hiatal hernia experience frequent acid reflux. The upward movement of the stomach reduces the pressure barrier. Consequently, acid reflux becomes more likely and more severe.
Not every person with a hiatal hernia develops GERD. However, the presence of a hernia increases the risk significantly. Larger hernias tend to cause more noticeable symptoms.
Understanding these links helps doctors plan better treatment. Lifestyle changes, medicines, or surgery may become necessary depending on the type and severity.