If acidic stomach contents flow back into the oesophagus, this is referred to as reflux or gastroesophageal reflux disease.

This can result in symptoms such as heartburn, belching, burning pain in chest, difficulty swallowing, acidic or bitter taste in the throat or mouth, hoarseness and cough. The most important examination for the diagnosis of reflux is gastroscopy. In most cases, drug therapy and a change in lifestyle lead to a significant improvement in the reflux symptoms. However, if the gastroscopy shows that the reflux disease is caused by a hiatal hernia (diaphragmatic hernia) with weakness of the sphincter muscle, in the long term only an operation usually helps to get the reflux symptoms under control.

Usually the lowest part of the oesophagus passes through the diaphragm into the abdomen. The oesophagus opens into the stomach directly below the diaphragm. At this transition, there is a sphincter (lower oesophageal sphincter) that prevents the contents of the stomach from flowing back into the oesophagus. The muscle tension of the diaphragm supports this closing mechanism. In the case of the most common hiatal hernia, the so-called axial hernia, the uppermost part of the stomach now enters the chest through the diaphragm. In this situation, the lower closure of the oesophagus can no longer be supported by the diaphragm and reflux occurs.