Why Would You Have to Drink Barium Sulfate Before a CT Scan?

For certain types of CT scans, barium sulfate is administered beforehand as a contrast dye to improve the clarity of the three-dimensional images, according to Medical News Today. Depending on the area of the body being examined, the contrast dye may be consumed orally, injected or taken as an enema.

Barium sulfate is typically used when scanning digestive organs, such as the stomach or esophagus, MedlinePlus notes. It is produced in liquid, paste, powder and tablet form. Similar to other contrast dyes, barium sulfate is classified as a "radiopaque" chemical because it coats the tissue linings of different organs without being absorbed, preventing X-ray beams from passing through it. As a result, this chemical shows up distinctly in images captured by a CT scanner.

A patient given contrast dye may be restricted from eating for at least four to six hours before the scan, according to MedlinePlus. However, barium sulfate and other radiopaque chemicals can cause allergic reactions, triggering symptoms such as throat swelling, difficulty breathing, hives, stomach cramps, diarrhrea and rapid heartbeat. When the physician considers it essential to use a contrast dye, regardless of allergies, the patient may need to take antihistamines to prevent symptoms. Since CT scans generally have built-in communication systems, patients can signal for help at any time if they experience serious discomfort.