Click on the colon carcinoma in the barium enema radiograph below:

The barium enema technique instills the radiopaque barium sulfate into the colon, producing a contrast with the wall of the colon that highlights any masses present. In this case, the classic "apple core" lesion is present, representing an encircling adenocarcinoma that constricts the lumen.

Below is a higher magnification of the radiograph above.