Barium

1. A metallic element belonging to the alkaline earths with an atomic number of 56 and an atomic weight of 137.34. The symbol for barium is Ba.
2. In medicine, refers to a chalky solution of barium used to coat the inside of organs, such as the stomach or intestines so that they will show up on an x-ray.

An enema using a white, chalky solution containing barium, in preparation for series of X-ray images of the lower intestine (colon). The barium outlines the colon on the X-ray image.

A test that involves filling the esophagus, stomach, and small intestines with a barium solution in preparation for an X-ray, to define the anatomy of the upper digestive tract. Also known as upper gastrointestinal series.