The negative side effects of a barium swallow X-ray include fecal impaction or constipation, says Johns Hopkins Medicine. This happens if the patient does not completely pass the barium. Barium is not water soluble and becomes stuck when the colon absorbs water from the stool, says PubMed Central.
The radiation from a barium swallow X-ray can also cause birth defects in a developing fetus and may increase the risk of problems in a person who has already been exposed to radiation, says Johns Hopkins Medicine. Patients who are allergic to contrast dyes might also have a reaction to a barium swallow X-ray, and need to tell their doctor of any sensitivities they may have. People who have a perforated bowel or esophagus, who are pregnant, or have a bowel obstruction should not undergo a barium swallow X-ray. People who have difficulty swallowing should also not undergo this procedure because of the risk of aspirating the barium into the lungs.
To help prevent fecal impaction from a barium swallow X-ray, the patient should drink lots of fluids after the procedure, says PubMed Central. She might also want to take milk of magnesia or other laxatives, and call the doctor if she doesn't have a bowel movement within 48 hours. A barium impaction is easily seen on an X-ray.