In medical dramas, all a doctor has to do is look at an x-ray, CT scan, or MRI to make a Lethal Diagnosis. It doesn't matter who the doctor is, what their specialty is, or if they're treating that particular patient. (In some instances, they might not even be a doctor - nurses and radiology technologists are just as prone to this as physicians.) The moment they hold the sheet of film up to the light box, their facial expression changes. This may involve a condition that is lethal and virtually untreatable like advanced stage cancer, or something that needs urgent attention like an intracranial hemorrhage or an aortic dissection. In more modern works, the personnel involved will be standing in the radiology control room as the images are shot, with the same horrified expression as the images result on the technologist's workstation. Ultrasound is also used for this purpose, typically in an Imperiled in Pregnancy plot, and makes for even more drama since the imaging is always acquired in real time and there isn't really any good way to avoid or delay the bad news.
A subtrope of Lethal Diagnosis.
- One Green Arrow story zig-zags this by having him get an x-ray after his ribs are bruised, and the doctor discovers that he's about to die. Halfway through the story, the doctor calls up to say there's been a mix-up, the x-ray actually belongs to... Oliver Queen! At the very end it's revealed that Ollie got speckles of radium on his chest from a broken watch before his x-ray and this botched the film.
- In The Fugitive the titular fugitive Doctor Kimble looks at the X-ray of a little boy and realizes immediately that the child is going to die if he doesn't get into surgery immediately. He fakes the necessary documentation, the kid is operated on and survives.
- On Scrubs, a doctor takes a look at a chest X-Ray and without knowing anything about the patient sees how advanced their lung cancer is.
"The owner of those lungs is gonna die, like, yesterday."
- On Monk episode "Mr. Monk And The Naked Man", a doctor looking at an X-Ray that had been hidden realizes that the guy has an aortic aneurysm that could burst at any moment.
- In the Supernatural episode "I Think I'm Gonna Like It Here" (S09, Ep01), a doctor looks at an MRI of a brain and an MRI of a knee and tells Dean that Sam has internal burns to major organs and is going to die.
- ER played this trope frequently, both the "plain film" and the "digital radiology" version. The "OB ultrasound" version was used quite a bit as well. (Occasionally it was even female staff running the ultrasound on themselves, either in service of a But I Can't Be Pregnant! or a Convenient Miscarriage plot.)
- Taken Up to Eleven as a very dark Running Gag on House, M.D.: every time a Patient of the Week was placed on the hospital's MRI machine, the magnetic resonance would either interact with the patient's disease somehow or the disease would pick that exact same moment to act up even worse than it had done so far on the episode, sometimes leading to the doctors to have to resuscitate the patient as he lies dying on the MRI's bed. It got to the point that the machine got the Fan Nickname of "The MRI Of Doom".
- On Adam Ruins Everything, the Expert of the Week explains to the patient in the episode that cancer doesn't work like everyone thinks it does...and that (if you aren't considered high-risk and haven't found a lump or anything like that), you really don't need to have an annual mammogram. She explains that all cancers are not equal: some progress or metastasize quickly (and when they are found, it's usually too late), some more slowly, and other tumors are benign (they don't metastasize, and are not fatal)...but mammograms cannot distinguish between these different tumor types, leading to false positives and overdiagnosis. Both of which are very hard on patients and families financially, and emotionally/psychologically, and may result in patients getting chemo/surgery/radiation/etc. that they don't need (because they either never had cancer, or they had a benign tumor), or the wrong type of treatment for their particular cancer. (Breast cancer isn't the only one with this problem, by the way.)