Likewise, the pyloric valve, the muscular ring between the stomach and small intestine, is supposed to open just enough to permit a fraction of an ounce of liquefied food to pass into the small intestine, but not enough to allow bile to back up into the stomach. When this valve fails to close properly, refluxed bile can cause gastritis, an irritation and inflammation of the stomach lining. Untreated, that can result in a bleeding ulcer or even stomach cancer.

If the oesophageal sphincter malfunctions at the same time, or there is a build-up of pressure in the stomach, bile and acid can reach the lower portion of the oesophagus, inflaming the delicate lining of this organ. If the problem persists, it can cause scarring that narrows the oesophagus, which may result in choking, or the cellular abnormality called Barrett's oesophagus, which can become precancerous and eventually develop into cancer that is nearly always fatal.

Gastroenterologists have recently demonstrated that Barrett's oesophagus can often be effectively treated with radiofrequency therapy.

Bile reflux can occur as a complication of certain surgeries, like gallbladder surgery.

More often, though, damage to the pyloric valve results from gastric surgery — total removal of the stomach or the gastric bypass operation used to treat morbid obesity.

Occasionally, the pyloric valve is obstructed by a peptic ulcer, for example, or scar tissue, which prevents the valve from opening enough to permit quick transport of stomach contents into the intestine. That causes pressure to build up in the stomach, pushing both acid and bile into the oesophagus.

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