In normal subjects, LES relaxes during swallowing. Even if it relaxes during other times, it is only transient. Also, since this sphincter is situated below the diaphragm, intraabdominal pressure and oblique entry of the oesophagus into the stomach further enhance its protective mechanism (Sawyer, 2005).
Reflux occurs when the LES- gastric pressure gradient is lost. The incompetence of LES may be either primary, or secondary due to various conditions like scleroderma, myopathies, pregnancy, female sex hormones, smoking, intake of smooth muscle relaxants, surgical destruction of LES, myotomy or balloon dilatation, and oesophagitis.
In hiatus hernia, the LES is pulled above the diaphragm and the sphincter mechanism is lost. In some patients, the sphincter effect is normal, but it relaxes inappropriately causing reflux (Scott, 1999). Stress and irregular eating habits aggravate reflux as in the case of Sally.
Once reflux starts occurring, the acidic gastric contents bathe the lower oesophageal mucosa and damage it causing oesophagitis. The extent of damage occurring depends on the mucosal protective mechanisms and the amount and duration of the refluxed material remaining in the oesophagus which in turn is affected by the frequency of episodes, quantity per episode, clearing of the oesophagus by secondary peristalsis and gravity and neutralizing the action of the alkaline saliva. Depending on the extent of damage the oesophagitis can be mild or erosive. In later stages, submucosal fibrosis can occur, leading to peptic stricture. Most of the times, these strictures are short and only in the lower oesophagus. Prolonged insult by the reflux contents to the squamous epithelium of the lower oesophagus can lead to Barrett’s oesophagus, wherein the mucosa develops into the columnar epithelium. This may be further complicated by a peptic ulcer or long peptic stricture (high up into the middle or upper oesophagus). .