The digestive system, (gastrointestinal tract), like other soft-tissue structures, does not show clearly enough for diagnostic purposes on plain radiographs. Barium shows clearly on a radiograph. If barium is swallowed before radiographs are taken, the barium within the esophagus, stomach or duodenum shows the shape of these organs.

Liquid suspensions of barium compounds are non-toxic, but they can cause constipation up to 48 hours afterwards. The technologist will remind you to drink lots of fluids for 24 hours after your test. They usually have a chalky taste that can be disguised by adding flavours.

A barium meal usually takes a very short time. The patient ingests gas pellets to expand the stomach. Barium is then ingested. The patient may move or roll over to coat the stomach and esophagus in barium. Following these preparations, an x-ray is taken. If the entire small bowel is required, the test can take significantly longer as the barium transits the bowel.

There are two varieties of barium meal: single and double contrast meals. A single contrast meal uses only barium to image the upper gastrointestinal tract. A double contrast meal uses barium as well as air, nitrogen, or carbon dioxide. The double contrast meal is more useful as a diagnostic test, demonstrating mucosal details and allowing the detection of small mucosal lesions such as diverticula or polyps.