Barium causes three types of gastrointestinal problems: (a) barium granulomas, (b) bolus obstruction, and (c) an allergic or anaphylactic reaction from the carboxymethylcellulose component of the barium sulfate suspension. Barium granulomas are nodules of histiocytes containing barium sulfate, usually localized to the gastrointestinal submucosa. Allergic reactions to barium sulfate affect less than two individuals per million (173). Perforation is an uncommon complication. When perforation occurs, it does so in several settings: (a) perforation following damage caused by previous mucosal disease, such as active colitis or diverticulitis (173,174); (b) mechanical damage caused by introduction of enema tips, balloons, and catheters; and (c) perforation in those with pre-existing diseases.