Which GI study should be scheduled last to avoid affecting other test results?

Correct option is C

A barium enema leaves residual contrast that can interfere with imaging results of other GI tests. It should be the last test scheduled. Explanation of options:
· (a) ✘ Ultrasound should be done before contrast use.
· (b) ✘ Done before barium to ensure visualization.
· (c) ✔ Must be scheduled last to avoid artifacts.
· (d) ✘ CT should precede contrast studies.