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Zebras, Not Horses


Zebras, Not Horses

Image from the National Park Service
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“When you hear hoof beats, look for horses, not zebras”. This is a principle most doctors learn in medical school. What it means, basically, is that a doctor should look to the most obvious for an answer, not the exotic. This may be a sound diagnostic principle, but for a subset of people who have rare diseases, it is perhaps not the most effective approach to medical care.

I speak, of course, from personal experience. Not only did it take four years for a doctor to decide that I had lupus, but there also was a span of about twenty years when I suffered, without treatment, mysterious episodes of acute abdominal pain. A whole herd of horses was pulled out to explain these episodes. But not until an emergency room physician insisted on taking a CT scan during one episode was a clue to my gut disturbances obtained. And not until a very astute and careful gastroenterologist studied these CT images was the puzzle further unraveled. It finally took my rheumatologist, a  creative and talented physician, to spot the zebra in the herd of horses: he determined that I was experiencing lupus-induced inflammation of the gut.

As idiosyncratic as lupus can be, there is still the conviction among many in the medical community that horses and not zebras predominate. In a Lupus Foundation article, for example, the transcript of a dialogue is presented. The dialogue is between Dr. David Isenberg , a noted gastroenterologist, and lupus patients. Dr. Isenberg explains to the patients the low probability that certain GI conditions will occur as a direct result of lupus. The doctor is asked about ascites (fluid in the abdomen), for example. He asserts that ascites are most likely to be caused by kidney or liver problems.

Of course, my experience refutes Dr. Isenberg’s perspective. Ascites was detected during several of my GI episodes. I did not have liver or kidney disease, although once I did have pancreatitis.

I came across another article which suggests my experience is not unique, though it certainly may not be common. In the medical journal RadioGraphics, which is dedicated to the field of radiology, I found the description of a young woman who had an acute episode of small bowel inflammation, with ascites. The woman also had systemic lupus. Her inflammation was successfully treated with high-dose steroids.

While Dr. Isenberg is an esteemed and accomplished researcher, in his interview he entertains as very remote the scenario suggested in the RadioGraphics article. Dr. Isenberg apparently not only expects to see horses, but he also recommends that everyone else does, too. This is not his “fault”; it is standard medical practice.

I have read that  sometimes ten years can pass between the time lupus is first suspected to the time when it is ultimately diagnosed. Perhaps the reason for this diagnostic lag has something to do with the horse/zebra dynamic. When dealing with an idiosyncratic disease like lupus, which can confuse and confound, maybe doctors should think more often about zebras. Because something is amiss in a protocol which leaves patients, for so long, without appropriate treatment.

I know that in the ordinary course of events, hoof beats will be produced by horses. But sometimes, when the possibility, or strong suspicion, of lupus exists, a doctor might consider the extraordinary. I think a lot of unnecessary suffering and true harm could be avoided if doctors would just allow themselves to look a little bit harder at what seems to be obvious.


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