I love medical riddles. (I don't mean the "Why-did-the-doctor-give-up-his-practice?" --"Because-he-lost-his-patien-ce!" kind of riddle).  I mean the kind that one wrestles with, the kind that is instructive, a teacher's tool, a way to make the student reason, formulate hypotheses, go to the book, research and eliminate possibilities . . . and come to the answer. Such riddles have a hallowed place in medicine--I remember these riddles only because I was asked them as a student and I learned something in trying to solve them.

So I'll often ask a medical student or resident, "Why do we say, 'Beware of the patient with a glass eye and a big liver?'" 

If the student were to reason this out, the steps ideally might go something like this:

I wonder why the patient had a glass eye in the first place.

I suppose it could be trauma . . .  could be a malignancy.

At this juncture the student might look up malignancies that occur in the eye and that justify removing an eye.

A melanoma in the eye is a common reason to remove an eye. (Or used to be--it has changed a bit with new treatment). 

Now . . . how might I connect this to a big liver? 

Hmmm. If melanoma metastasized to the liver, then they probably would never have taken the eye out in the first place and replaced it with a prosthetic eye.

At this point the student might look in a textbook or in UpToDate and find that ocular melanoma is famous for recurring years later with distant metastases. When it does return it often presents with new tumors in the liver. Bingo!

Ideally that's how a student would reason. If however the student were to decide to "google" the question by typing in "glass eye and big liver" as I just did, the first hit is NEJM: Solution to a Medical Mystery, which gives the answer to a photoquiz the New England Journal of Medicine put in its pages in 1997, showing an elderly lady with one eye that was clearly yellow with jaundice and the other which was pearly white. (The latter had to be a glass eye because there is no earthly reason for jaundice in just one eye. And she was jaundiced because she had melanoma metastases in the liver.)  A total of 928 readers had the correct answer.  No surprise I suppose because it's an old riddle.

If the Journal were to repeat the photoquiz with a similar patient in the years to come, Google would lead the readers right to the answer.

Which is why when I offered a new riddle to my students last week while we were rounding, I emphatically added, "Don't Google!" Nothing at all against Google--we're proud of Google at Stanford, and indeed my kid brother works there. But the point of the riddle is to search your brain, not Google. To reason and to come to the answer for the right reasons . .  not just to come to the answer.

In case you're curious, the riddle I gave my students and which they are supposed to report on this week is:

A man walks into a bar, offers to keep his head completely submerged in a bucket of water for twenty minutes and if he doesnt he will buy drinks all around and if he does the patrons must stand him a round of drinks. He does and so they do. The question is how did he do it?  

A clue? No hidden tracheostomy, and yes it's a medical condition that allows him to do this.  And remember, don't google this riddle!