The stomach normally resides in the abdomen, where is acts as an organ for the initial storage and digestion of ingested material. The oesophagus, which travels from the back of the mouth, through the neck and the entire length of the chest normally joins the stomach just within the abdomen, passing through a muscular sheet between these two body cavities called the diaphragm. Correct anatomy of this arrangement is crucial in maintaining the normal function of these complex organs
Two types of hiatal hernia are described: A
sliding hiatal hernia means that the stomach slips up and down from the stomach into the chest and back; a
paraoesophageal hernia describes the condition in which the upper part of the stomach, including the junction of the oesophagus and stomach (oesophago-gastric junction, OGJ) is all in the chest and stays there. In some cases, a hiatal hernia can get stuck in the chest (incarcerated) and this may then lead to a cut-off in its blood supply (strangulated), particularly if the stomach becomes twisted (gastric volvulus). This condition is seriously life threatening without emergency surgery.
The presence of a small hiatal hernia is very common, and symptoms are essentially that of reflux disease. As hiatal hernia get larger, they can start to cause more serious problems. Reflux symptoms, particularly regurgitation and dysphagia become more intolerable, and this can lead to aspiration of gastric contents into the chest causing infection and pneumonia. Breathing itself can become compromised because of the space that the stomach now occupies within the chest. The part of the stomach trapped in the chest can get inflamed, causing bleeding and anaemia, and if the blood supply gets cut off, then the stomach itself is at risk.
For more information on these conditions including FAQ's go to 
