What diagnostic test should be scheduled last due to its use of a specific medium?

The barium enema (BE) should be scheduled last among the listed diagnostic tests due to its reliance on a specific medium, which is barium sulfate. This contrast agent is used to enhance the imaging of the intestines during the procedure. It is crucial to perform tests that do not require the use of any contrast medium beforehand, as it is important to avoid any potential interference with the imaging results of the barium enema. For example, a CT scan or an X-ray may utilize contrast agents as well, and having them conducted before a barium enema could diminish the clarity and quality of the images obtained.

Proper scheduling is essential to ensure accurate diagnostic imaging. Therefore, scheduling the barium enema last allows for any residual contrast media from preceding tests to clear, thereby preventing overlap that could obscure the imaging of the bowel on the barium enema.