Principle
Barium sulfate is a type of contrast medium that is opaque to X-rays. As the patient swallows the barium suspension, it coats the esophagus with a thin layer of the barium. This enables the hollow structure to be imaged.
This is commonly used with baking soda (sodium bicarbonate crystals) to produce gas (see Reactions of sodium bicarbonate). As gas is low in density, and the X-rays pass through very easily, they will appear as white patches, as opposed to the black produced by relatively dense, X-ray opaque barium. As such, it is extremely useful in providing a contrast to the barium, to produce a double contrast image, to allow better visualisation of the contrasting features within the mucosal layer of the esophagus.
Barium sulfate is an irritant outside the gastrointestinal tract. In cases where a leak is suspected or desired to be demonstrated, contrast imaging involving the use of water-soluble contrast media containing iodine is used.
As with all X-rays, the barium swallow technique employs radiation, and may irradiate the patient unnecessarily. The barium swallow should not be used unless required, and, although it cannot be replaced by endoscopy as for the barium enema, it should be avoided as much as possible for children and pregnant women.
Read more about this topic: Barium Swallow
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