Yup, if it walks like a duck, and quacks like a duck, it’s probably a duck. That’s one of the many medical aphorisms that I found true enough to include in my shopping bag of things to think about when considering a diagnosis. In other words, particular illnesses have hallmark characteristics. Let’s take influenza as a convenient example: high fever, body aches, headache, prostration (medicalese for “can’t move far enough to pick up the telephone”), zero appetite. Sound familiar? Yup, we could all hit a bullseye on that one from across the room. It walks like a duck and quacks like a duck.
The corollary to the “duck” aphorism is, “When you hear hoofbeats, don’t think of zebras,” which is a fancy way of stating “common things are common.”
So, to keep with out flu example, if you had a patient with high fever, racking chills, body aches, etc., you would think of the flu, rather than, say, malaria, unless you were in Africa or some place where malaria was common. It is not common in most of the Western world, so that would not be at the top of your diagnosis list.
On the other hand, I had a patient in the ER once, a beautiful 17 year old black Haitian boy, who had a fever of 105, racking chills, body aches, and a pulse of 60. Normally the higher our temperature goes, the faster our pulse goes to pump blood around the body to help get rid of toxins. So a fever of 105 and a pulse of 60 is already a paradox.
Oh, excuse me for forgetting to tell you: the boy was schizophrenic. That’s important.
I drew some blood, which looked consistent with an acute infection. Then I went to the hospital medical library. In those days they had actual books. I found the answer there, in an infectious disease text book from the 1950′s: it was typhoid fever, which you get drinking contaminated water.
I called the infectious disease consultant, all excited and proud of myself for making a cool diagnosis. I read her the patient’s chart on the phone. I got to the part about his being schizophrenic, and I though the line had gone dead, there was such a long silence.
“When you hear hoofbeats, don’t think of zebras. He has the flu,” was the flat response.
“He can’t have the flu. His pulse is 60. It should be at least 120 or more. His blood count is through the roof. He has an acute bacterial infection of some kind.”
(Snottily): “Well, if you really think he’s toxic, give him two grams of I.V. Ceftriaxone and send him home. Have him follow up with you in two days.”
I didn’t feel good about the whole thing. I drew blood cultures and gave the strong antibiotic, and watched him for another four hours. The fever did come down, and he actually looked great after the antibiotic.
Two days later he came back looking much better. He was actually able to talk now. He told me that he’d been to Haiti on vacation with his mother for a month, and just returned two weeks ago. I examined him, and the only unusual thing on exam was that the whites of his eyes were yellow. That means there is something wrong with the liver.
I called the lab and had them fax me all his results stat. Hah! The blood culture results were positive for Salmonella Typhi! He had Typhoid Fever. Now we had a problem, though. Giving the wrong kind of antibiotics at the wrong time in Typhoid can drive the bacteria into the liver, where they can live for years, making the patient a chronic carrier, like Typhoid Mary. So I had to call the snotty Infectious Disease consultant again.
“Hey, you know that schizophrenic kid from the other night? The one with the flu?”
“Well, his blood cultures are positive for Salmonella Typhi. He’s got Typhoid Fever.”
“Who the hell told you to get blood cultures?”
“Nobody. I just thought it was strange that he had a paradoxical pulse with a fever of 105, so I looked it up. You know what they say: if it walks like a duck, and quacks like a duck..” The phone went dead.
Five minutes later, the snotty Infectious Disease specialist was at the patient’s side, examining his liver and everything else. She wrote a case report in a prominent medical journal about the “Zebra” patient we had. My name never appeared in the article, of course.
Oh, drat, I did it again. I have a personal reason for writing these posts, but I haven’t written it here. Got too wrapped up in the Typhoid case. I’ll try to do better tomorrow.