Forget, for a moment, the show/tell thing. Look at it instead as an infodump/lack-of-conflict issue.
In real life, the patient goes to see the doctor, sits around in the waiting room for an hour, goes into another room with a nurse to have blood pressure taken, goes into another room to wait for the doc, meets with the doc, gets scrips/referrals and heads off to the lab to have blood drawn, and down to the x-ray department for x-rays or whatever other tests are being done.
You're yawning, now, right? It's boring. And not what fiction is made of. Fiction is conflict.
When turning that reality into fiction, the author picks and chooses the defining moments, the times of change-inducing conflict, the times that show -- not medical stuff, but -- the key moments of the plot, where the character is changing and growing and struggling.
So, using the list of stuff I've got above, the author is most likely going to skip the waiting room, the blood pressure check, the wait in the exam room, everything up to the doc's arrival, or, at best, reference it in a brief, "two hours after she'd arrived at the clinic, the doc walked through the door." Or, if the waiting room is shown, it won't be along the lines of "Protagonist fidgeted in her seat for two hours, worrying and obsessing about how soon she'd die." It would be more along the lines of a conversation between the protagonist and the friend who accompanied her to the doc's office, and who's trying to convince her to do something (e.g., cheer up, think positively, or accept her diagnosis, or move to Tahiti and die in beautiful surroundings, or whatever, something that will affect the protagonist's choices over the course of the book).
Even the scene with the doc wouldn't likely be the full interaction between doc and patient (or then again, maybe it would; I had a kidney ultrasound yesterday, and while the entire process took about 45 minutes, the doc was in the room perhaps 3 minutes, and the conversation would've made a teeny-weeny scene), but will focus on the key moment, the key exchange, the thing that moves the plot forward and causes the protagonist to struggle and ultimately to make a decision.
What happens in the scene depends less on a real-life's likely encounter than on the uniqueness of who the protagonist is, and where she is in the plot and the stage of her character development.
Let's say she's going to develop from denial to acceptance and triumph over the course of the book.Then the key to any scene in the early part of the book, prior to acceptance, is going to be her struggle to stay in denial, and the opposing character's attempts to get her to accept reality and to participate fully in her treatment. In that case, the doc comes in all somber and pronouncing how grim things are, and she's all flip and wisecracking, and he explains a little about the process, and she cuts him off because she doesn't want to know, and he insists on telling her more, and so on.
You make the explanation part of the conflict, part of the struggle between the two characters in the scene. Ramp it up from what woiuld happen in real life, where it would be a lot less dramatic, although we'd all react in our unique ways. I, for example, am a huge obsesser and need to understand everything about my health issues (I'm a firm believer in having some control over my own health), so I research everything before I go see the doc, and then can skip the basics and get into the nitty-gritty, and I look at the MRI results on the doc's computer, and afterwards I get copies of all my lab tests and so on. Other people (and this really freaks me out, b/c I can't imagine doing it myself), prefer not to know any of "that medical stuff" and just tune out when the doc starts using words that end in "pathy" and "osis" and the like, and just say "do whatever you think is best," and don't have a clue what drugs they're taking or what the possible side effects are. (Yeah, I actually read all the small print in those little pamphlets that come with prescription drugs.) And some other people have pre-set decisions, like "I will never have surgery" or "I will never take X drug" or whatever. The reactions are individual and varied, and if you set the scene up so that the patient's reaction is inconsistent with what the doc wants, you've got conflict, and can present information without infodump.
JD