A hiatal hernia is a prolapse of part of the stomach through the opening (hiatus) of the diaphragm in the chest. Normally, the hiatus is a small opening in the diaphragm through which the esophagus passes just before it joins the stomach. As a result, nutrients and acidic contents of the stomach can return unhindered to the esophagus and cause burning for the sternum, and subsequently inflammation of the esophagus (esophagitis), which causes the so-called gastroesophageal reflux disease (GERD). Hiatal hernias grow larger over time, and it is possible for the entire stomach and even other organs to enter the chest.

There are 4 types of hiatal hernia:
-    Sliding (axial) hiatal hernia;
-    Paraesophageal hiatal hernia;
-    Mixed type; Complicated hiatal hernia, in which, in addition to the stomach, there is also another abdominal organ in the chest (colon, pancreas, spleen, etc.).