Saturday, June 30, 2012


Today I am sitting in my office in the clinic.  It's one of the good days when I have a chance to catch up on paperwork and charts.  I need a break, so I'm going to discuss zebras.

There are a few great sayings that help us make reasonable and accurate diagnoses.  The first is this:

"Uncommon presentations of common problems are much more frequent that common presentations of uncommon problems." 

The second is this:

"When you hear hoofbeats, think "horses," not "zebras." 

A zebra in North America is a rare beast, indeed.  At the same time, they sound like horses as they run across the savannah.  Both animals have hooves that are quite similar.  If you saw one from afar you might think they are quite similar looking; if you just caught the silhouette of the animal against the sun then you could easily mistake a horse for a zebra or vice versa.  Thus we use the metaphor of zebras vs. horses to keep our heads on straight. 

When a patient comes in complaining of nausea and vomiting you think that she probably has a stomach bug because this is the most common thing - the horse - that will cause her symptoms.  As a PA I gather her history, perform a physical exam and look for any signs that there could be something else going on.  I put the puzzle together.  There are a hundred things that can cause nausea and vomiting, so how do I know it's a simple case of food poisoning or a stomach virus she picked up from her grandchild?  I listen to the history, confirm it with a physical exam that rules out most of the other 99 things that it could be, and - shazam! - I make a diagnosis.  And yet occasionally....  Very occasionally....  I will catch a zebra.  Like the patient who comes in with nausea and vomiting as the primary complaint and, "Oh... by the way...  I have a little rash on my leg."  Some of my patients have the oddest little, "Oh, by the way..." symptoms.  Some that I've heard have included, "My tongue is all bumpy," "When I move my head like this, I sneeze," or, "When I press really hard on my face right here, it hurts."  To these three I reply, "everyone's tongue is bumpy," "then don't do that," and, "everyone's face hurts when they push hard enough to leave nail marks like you are doing right now."  But how do I weed out the random garbage from the real stuff?

The answer to that question really is the million dollar question.  And I'll be honest: I don't always have a good way to weed it out.  There are some conditions in which all of the signs point one direction yet there is that little piece of the history that bugs me.  It's like a frustrating, nagging buzzing in the back of my mind that leads me to look one step deeper - order one more test or one more image or examine one more part of the patient.  It's just that one thing that doesn't fit with a horse-type condition; it's that one symptoms or physical finding that, if truly present, makes this condition into a zebra.  Then again, there is the occasional nagging oddity that may prompt me to look deeper still - but then I find nothing.  I diagnose them with a common problem - a horse - and they go home only to have the zebra rear it's head and show itself in all its striped glory just hours after leaving my office.  Again, in honesty, this is the most frustrating thing I've ever experienced. 

So there you have my musings on zebras for the day.  They're rare, I try to look for them.  Often they are elusive, and if I'm lucky I'll catch onto the one thing that doesn't fit.  The one thing that shows the zebra for what it truly is.  Which brings me to another saying that I've often heard along the way:

"It's better to be lucky than good."

And I have to agree.