“How often have I said to you that when you have eliminated the impossible, whatever remains, however improbable, must be the truth?”
—Sherlock Holmes in “The Sign of the Four” by Sir Arthur Conan Doyle
Smart guy, that Sherlock Holmes. He simply went around making observations, putting things together, coming to a reasonable conclusion—he was a radiologist! I knew it. I have friends/colleagues/acquaintances who aspire to be Sherlock. They want to bust a case open and they are on the hunt for the most potentially obscure diagnosis they can come up with. You know these people, I’m sure.
You know the saying, “You are more likely to see an uncommon presentation of a common disease than a common presentation of a rare disease”? How many of you know people who work at that the other way? They think they are more likely to see an uncommon presentation of a rare disease than a common presentation of a common disease. And then they do the Sherlock thing and look for clues.
Looks like (fill in the blank). Something you see every day, maybe three or four times. You pick up the microphone to dictate. Sherlock Jr. is over your shoulder (no work for them to do, so they want to check in on yours). “Wow, great case, eh? Is that (fill in your favorite odd/rare/faintly remembered disease)?”
“No,” you say. “It’s (common disease). Why would you say that? Doesn’t that always look heinous?”
“Well,” they say. “Occasionally it can look like (common disease), and you need to check their serum (weird lab study) to confirm.”
You do the smart thing. You ignore them. You dictate. They put on the hat and pipe and get down to some serious detective work.
“Hey, their bilirubin is marginally elevated. That could be seen in (odd disease) and their hematocrit is also marginally low, another good hint, and the age is exactly right,” they say.
“I am through with that case, dictated and finalized,” you say. But then, a responsible clinician (with similar Sherlock inclinations, invariably) comes into the room and Sherlock Jr. takes over. And then, my friends, the labs and studies go ballistic. Fast forward a day or so, everyone agrees the case is nothing more than (common disease). You have my permission to feel vindicated. I think that some people want to diagnose that one weird, rare disease to make their career.
Sherlock made some fabulous calls, but he didn’t ignore the obvious—he used it as an exclusionary criterion. As one of my clinician friends often said, “If it walks like a duck, quacks like a duck, and looks like a duck, it’s a duck.” Even Sherlock would agree.
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CD Phillips. Wet Read: The radiologist as detective, part 2. Appl Radiol. 2015;44(10):32.
Dr. Phillips is a Professor of Radiology, Director of Head and Neck Imaging, at Weill Cornell Medical College, NewYork-Presbyterian Hospital, New York, NY. He is a member of the Applied Radiology Editorial Advisory Board.