A hiatal hernia is a medical condition in which the upper part of the stomach or other internal organ bulges through an opening in the diaphragm. The diaphragm is a muscular structure that assists in respiration and has a small opening, a hiatus, through which the esophagus passes prior to connecting to the stomach. This is called the gastroesophageal junction (GEJ). In a hiatal hernia, the stomach pushes through that opening and into the chest and compromises the lower esophageal sphincter (LES). This laxity of the LES can allow gastric content and acid to back up into the esophagus and is the leading cause of gastroesophageal reflux disease (GERD). While small hiatal hernias are often asymptomatic and can typically be managed medically, large hiatal hernias often requires surgery.
Classification of hiatal hernias are divided into 4 types:
Type I (sliding type), which represents more than 95% of hiatal hernias, occurs when the GEJ is displaced upwards towards the hiatus.
Type II is a paraesophageal hiatal hernia, which occurs when part of the stomach migrates into the mediastinum parallel to the esophagus.
Type III is both a paraesophageal hernia and a sliding hernia, where both the GEJ and a portion of the stomach have migrated into the mediastinum.
Type IV is when the stomach, as well as an additional organ such as the colon, small intestine, or spleen, also herniate into the chest.