How Do Doctors Solve Medical Mysteries?

How do doctors make a diagnosis when the symptoms aren't obvious? House Call Doctor plays "House" to solve a patient's perplexing condition.

Rob Lamberts, MD
6-minute read
Episode #47
confused doctor

Diagnosis Step 5: The Exam

Once we’ve done all that data-gathering, doctors finally get to the physical exam. By the time I examine people, I have a good idea of what I am looking for, but I still try to do a thorough exam. In this case, I pay very close attention to Frank’s lung exam, listening for anything abnormal. His exam is entirely normal.

Diagnosis Step 6: The Differential

So now we come to the climax of the drama. How does the doctor put all of these pieces together to make a diagnosis? Does the doctor fall prey to his prescription drug addiction and miss important facts? How many people will the doctor insult in the process?

Actually, it’s not quite that dramatic. The real next step is to do something simple: make a list. Doctors call this the differential diagnosis, which basically asks two questions:

  1. What are the bad things that I have to rule out?

  2. What are the other things that could cause the symptoms?

The ability to build a good differential is key to being a good diagnostician. For a chronic cough, lung cancer and tuberculosis are the two main bad things I need to rule out. Since Frank is young and a non-smoker, the risks are quite low and therefore worth considering only after more common things are ruled out. There are four common causes of a chronic cough:


  • Drainage from the sinuses
  • Esophageal reflux
  • Asthma
  • Medications (specifically, a very common blood pressure medication called an ACE inhibitor is associated with an annoying dry cough.)

In this case, the patient has no drainage from his sinuses, and doesn’t have asthma. That doesn’t rule these things out, but it does make them less likely. He is a firefighter, so his exposure to smoke could make him more susceptible to lung symptoms. He does have heartburn occasionally, so reflux is still on his list. My initial suspect, the blood pressure medication, turns out being innocent, as he is not taking an ACE inhibitor.

The Mystery Diagnosis

So we are left with reflux being the top thing on the list, with sinus drainage and asthma being much lower down. Instead of ordering a chest x-ray, or other expensive tests, which wouldn’t help with any of these problems, I would treat Frank for reflux and see whether his cough went away. If it does go away, we’ve got our answer; if it doesn’t, then more work-up is required.

Well, he didn’t get better after two weeks of the reflux medication, Prilosec, so I examined him again and this time noted a piece of dirt in one of his ear canals that I must have missed before. When I attempted to remove it, he coughed uncontrollably, so we had to wash it out with water. After that, his cough went away.

There is a nerve in the ear, called Arnold’s Nerve, which is a branch of the nerve that controls the diaphragm. In some people, stimulation of this nerve will make them cough. I’ve actually seen this a few times in my office.

Now you know all of the steps a doctor must go through to diagnose you. My advice for you, as a patient, is to be prepared for these steps before you actually see the doctor. That way you can give the doctor all of the important information they need to make an accurate diagnosis. 

Click here to read the second installment in my mystery diagnosis series, in which I get to the bottom of a patient's dizziness.

If you have topics or mystery diagnoses, that you want me to discuss, send them to housecalldoctor@quickanddirtytips.com, or you can submit them to me on Twitter or my Facebook page.

Let me once again remind you that this article is for informational purposes only. My goal is to add to your medical knowledge and translate some of the weird medical stuff you hear, so when you do go to your doctor, your visits will be more fruitful. I don’t intend to replace your doctor; he or she is the one you should always consult about your own medical condition.

Catch you next time! Stay Healthy!

Doctor image courtesy of Shutterstock


Medical Disclaimer
Please note that all content here is strictly for informational purposes only. This content does not substitute any medical advice, and does not replace any medical judgment or reasoning by your own personal health provider. Please always seek a licensed physician in your area regarding all health related questions and issues.