The patient drinks a contrast medium containing barium sulfate. This contrast medium appears white on x-rays, and shows the outline of the internal lining of the bowel. X-ray images are taken as the contrast moves through the intestine, commonly at 0 minutes, 20 minutes, 40 minutes and 90 minutes. This enables the radiologist to assess the bowel as it becomes visible. The test is completed when the Barium is visualised in the terminal ileum and Caecum, which marks the beginning of the large bowel. This is one of the most common places for pathology of the bowel to be found, therefore imaging of this structure is crucial. The test length varies from patient to patient as bowel motility is highly variable.
The barium is non-toxic and passed out normally as a stool, although the appearance may be paler than usual.
The Barium follow through test is used to diagnose conditions of the small bowel, most commonly Crohn's disease. This shows up as intermitent sections of strictured bowel. Other bowel pathologies which are picked up on this test include: