The lower end of the oesophagus is closed by a functional valve formed by the crossing over of elements of the diaphragmatic muscle around the oesophagus. The valve is commonly imperfect in effect, and in latter times in rich countries much more commonly imperfect.
Acid and other stomach contents therefore may move from the stomach to the oesophagus.
The lining of the stomach is adapted to resist acid, but the oesophageal mucosa is not, and damage results if it is exposed to considerable contact with acid.
Acid may reach the pharynx, and spill over into the airway, providing one cause of chronic cough. Oesophageal manometry with pH telemetry investigates this.
Explanation, advice and modification of adverse factors of habitus and lifestyle ("eat less and not so late until you are lighter") are very often sufficient. A rafting antacid mixture or a proton pump inhibitor or both are the usual escalation.
Surgical treatment, with various fundoplication operations such as that after Nissen is rare and non-trivial but is likely to be effective.
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