Which x-ray exam uses an opaque contrast medium to examine the lower GI tract?

• A. Barium Swallow
• B. Angiography
• C. Barium Enema
• D. Amniocentesis

Answer: (C)

When you want to see the inside lining of the lower GI tract on X-ray, you need a study that fills the colon with a radiopaque liquid so the walls and any irregularities show up clearly. This is a barium enema: a barium-containing solution is introduced through the rectum to coat and distend the colon, making it visible as a bright outline on the X-ray. This allows evaluation of the colon and rectum for polyps, diverticula, strictures, or other abnormalities. The other options focus on different areas or uses: a barium swallow images the upper GI tract (esophagus and stomach), angiography looks at blood vessels using contrast, and amniocentesis is a prenatal procedure not involving GI imaging.