What is a hiatal hernia?

A hiatal hernia occurs when a portion of the stomach bulges through the diaphragm into the mediastinum, the central compartment of the thoracic cavity. This anatomical alteration allows the stomach to extend above the diaphragm instead of remaining fully in the abdominal cavity, which can lead to various symptoms, such as gastroesophageal reflux disease (GERD), chest pain, or difficulty swallowing.

Understanding the structure of the diaphragm is essential, as it serves as a muscular barrier between the thoracic cavity and the abdominal cavity. In a hiatal hernia, this barrier is compromised, allowing stomach contents to potentially flow back into the esophagus, contributing to the discomfort typically associated with this condition. This condition can be classified into two types: sliding hiatal hernias and paraesophageal hiatal hernias, each with distinctive characteristics and implications for treatment.

The other options describe conditions unrelated to hiatal hernias, as they pertain to different anatomical structures or diseases entirely. Therefore, the definition and implications of a hiatal hernia are best captured in the description of the protrusion of part of the stomach into the mediastinum.