Hernias are usually associated with overstraining. However, a hiatus cannot really be said to be caused by anything that you might have done, except perhaps overeating to the point of obesity. Nonetheless, its symptoms are all too real to those affected and can be painful in the extreme.
It is important to understand the anatomy of the chest area before grasping how a hiatus hernia comes about. The stomach lies immediately under the diaphragm, a muscular sheet which separates the chest from the abdomen. The gullet (oesophagus) passes through a small opening in the diaphragm in order to reach the stomach. Normally, the stomach end of the oesophagus and its muscular control ring (sphincter) lie just beneath the diaphragm. When the stomach is distended, pressure pushes upwards against the diaphragm and this closes the sphincter, preventing the stomach contents from passing back up into the gullet.
Sometimes, however, the junction of the gullet and the stomach slips up through the oesophageal opening in the diaphragm and into the chest. This is called a hiatus hernia and the main effect is that the mechanism which prevents regurgitation into the gullet cannot operate properly and so the acidified and highly irritating stomach contents are able to move up into the gullet, damaging the lining and causing a condition called esophagitis.
Hiatus hernias are most common in middle-aged and elderly women, especially in the obese. They cause severe heartburn (a deep burning pain behind the breast bone) made worse by bending forward, by straining and by lying down. The pain is so intense that it often disturbs sleep and can be mistaken for a heart attack. Other symptoms of hiatus hernia and the associated esophagitis include acid in the mouth (water brash) and difficulty in swallowing. Sometimes, the condition is complicated by ulceration, bleeding, scarring, and narrowing of the gullet. In such cases, anaemia can result from blood loss. Long-term hiatus hernia can cause dangerous changes in the cells lining the oesophagus and some authorities believe this may progress to cancer.