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It is said that the only things guaranteed in life are “death and taxes” and while some have been known to avoid taxes, death will eventually claim us all. Indeed, not all of us are doctors but we all have been, or will be, patients. For the past five years I had had the privilege of presenting the Mini-MD, a comprehensive overview of all of medicine (some call it a “Mini Medical School) for healthcare professionals worldwide, teaching the program at Samsung, both in Korea and in the U.S., and then more broadly in Singapore, Melbourne, Italy and later this month (October 22nd) back in Seoul. The program is designed for those in the healthcare field, though without formal medical training: they include hospital executives, pharmaceutical and medical technology leaders, government policy makers, biomedical scientists and engineers, healthcare designers, lawyers, etc. But if you think about it, medicine, for the main reason given above, that it affects us all, is of deep, enduring interest. The human body holds endless fascination, and even more so in the case of disease, and acutely so when it affects us. So how is it that doctors think? How do they arrive at diagnoses? Is it a science—or an art? Some of us may just defer to doctors and leave it at that, but most, especially as we approach our inevitable mortality are more than curious. So I thought I would share here, for the benefit of my fellow KBLA members and wider audience, some of the distilled “pearls of wisdom” on how doctors think. Reading further may not save your life, but, who knows, it might very well do just that …

From the General to the Specific

Obviously, we will not cover all of medical school in the space of a few paragraphs but there are some general principles that doctors follow, some of it learned explicitly, others more subconscious. One is the concept of proceeding from the general to the specific. While the structure of medical practice is often oriented towards specialty care (indeed, many people complain that some doctors seem to care only about specific diseases and organs, and not the whole person), medical education is fundamentally general and broad. In the United States, medical school is actually called “undergraduate medical training”, much to the chagrin of college graduates who have already gone through “undergraduate” training, only to have to do it again!! What that means is that all doctors are actually trained to be generalists – there is no “medical school for the liver” or “medical school of cardiology”. Rather, we are exposed to all the aspects of medicine, from superspecialized surgery all the way to the basics of labor and delivery in obstetrics, all in an effort to instill the principles of care for the whole patient, and in the scientific sense, to minimize diagnostic mistakes that arise from overspecialization.Here’s an example. Say you have a cough: a lay person may logically conclude that the problem is with the lungs. It is the lungs, after all, that are producing the “cough”. Of course, most will do a Google search and if you go to some reputable site you’ll find a long list of possible causes (“etiology” is the technical term) of cough. But a doctor — a good doctor — will be trained to look at the broad range of possibilities first, and then narrow these down more specifically based on information, data, results of tests, and so forth.

The Logic of Medicine: How Doctors Think

Ogan Gurel, MDCEO, NovumWaves

ogan.gurel@kbla.info

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So, roughly speaking, there are actually three anatomic sources of cough (we would call this the “differential diagnosis of cough”) and they would be the lung (no surprise), the heart, and the stomach. [More on this later, but the heart can cause a cough via “heart failure” in which fluid backs up into the lungs, thereby causing the cough-inducing irritation, and the stomach can incite cough through gastroesogpheal reflux, namely stomach acid getting into the esophagus and creeping up to the lung.] Of course, not everything causes cough. It would be very unusual indeed if one of the anatomical causes of cough were your left big toe. So part of the science and art of medicine – the reason for the long training, is how general to be and how quickly to get specific. Too general, and you waste time, money, and create potential risk for patients, investigating things pointlessly. Too specific, and you run the risk of misdiagnosis some, if not most, of the time.

This principle of general to specific also pervades the process of medical diagnosis, indeed the entire engagement with the patient. As

most people know, on first encounter with a doctor, typically (and there are exceptions such as emergencies, general screening tests, etc.) the relationship begins with a conversation (formally called “taking the history”). “What brings you to the hospital?” or “What is bothering you today?” are typical questions that are posed to elicit what is called the “chief complaint”. After taking the history, a physical exam is performed which begins to get more specific in its focus, after which blood tests are taken, again guided towards more specific results, and perhaps some other tests or imaging studies. The sequence is not random. One does not show up at the hospital and immediately get a test for, say thyroid disease, and then a colonoscopy, and eventually a doctor shows up and gets around to asking what the problem is. From the general to the specific is the guiding principle. It may not always happen that way, but that is the ideal.

Framing the Problem: Dualities

So let’s say you’ve seen the doctor with your cough and they determine it’s not the heart (for example, some

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specific heart related tests come back negative) and neither do you have reflux (heartburn). So it’s likely to be a lung problem. Lung disease: now that, too, is fairly broad and often, when faced with a broad spectrum of possibilities, doctors will frame the problem in terms of a duality, namely two contrary possibilities. It turns out that there are two types of lung disease: obstructive lung diseases and restrictive diseases. And this way of categorizing medical knowledge as dualities is extremely common. For example, there are two types of heart failure: systolic heart failure (poor pumping of the heart with blood) and diastolic heart failure (poor filling of the heart with blood): even though both are “heart failure”, they have entirely different causes and treatments. Stroke comes in two varieties: ischemic stroke (lack of blood flow to the brain) and hemorrhagic stroke (bleeding or too much blood to the brain), for which the treatments are obviously quite different. In fact, the treatment of ischemic stroke, life saving in that instance, could very well be fatal if applied to a patient with hemorrhagic stroke. So these dualities are not just theoretical constructs but have very real implications and consequences.

Back to the cough. In obstructive lung diseases (such as bronchitis or asthma) it turns out that the lung volumes are actually larger than normal, which makes sense as the obstruction, such as with narrowed airways, prevents air from being adequately blown out. In fact, doctors can often spot a patient, even without tests, as potentially having obstructive lung disease, if they show up with a large “barrel” chest, a consequence of a chronic (long-term) obstructive process. But again, more specific tests, such as spirometry or so-called “pulmonary function tests” (the one in which you are told to breathe in and out of a tube) can pick this up more specifically. Restrictive lung disease, which is generally rarer, is characterized by smaller lung volumes, as you can see from the

diagram. Again, as with the heart failure or stroke examples, the further diagnostic steps and treatment options are entirely different for these two categories.

Dualities are very important in providing structure to medical knowledge and framing the problem. The offer certainty, an “either / or” kind of thinking that is very important in proceeding to the beyond just the vague amorphousness of “lung disease”. Knowing and understanding these dualities is a key part of medical training.

Prior Probabilities

Of course, medicine, and life in general, is not so “black and white”. As is commonly taught, medicine is not an exact science and while frameworks such as the ones I shared above offer some degree of certainty, nothing is more certain than the possibility of uncertainty. But there is a science of uncertainty, which falls under the general scheme of statistics, but in the case of medicine (and other fields) deals more specifically with the concept of “prior probabilities” codified in a mathematical law called “Bayes Theorem”. Without being too technical, Bayes Theorem (the science of “conditional probabilities” or “prior probabilities”) basically states that the probability of an event (say a certain diagnosis) is related to conditions that are related to that event. Let’s look at the probability of a pregnancy test being positive. If one already knows that the patient is male (e.g. a “prior probability” obtained via the history or observation), then we already know, we are certain, that is, that the probability of the pregnancy test being positive is zero. Of course, that is an extreme example but most of medical diagnosis is influenced strongly by such thinking. This is one reason why the “general” approach outlined above, and, in particular, good “history-taking” is so essential to getting the right diagnosis. Lay persons often thing that one single blood test “clinches”

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the diagnosis, but in reality is a combination of data points, each of which create the circumstances for greater certainty (e.g. “conditional probabilities”) which would otherwise be impossible. It’s one of the reasons why we don’t screen everybody for cancer, for the same reason we don’t screen men for pregnancy. The prior probability of a 5-year non-smoker getting lung cancer is so infinitesimally small that it is far outweighed by the risk, cost, and inconvenience of submitting that toddler to a CT exam. It may sounds like an oxymoron, but prior probabilities ensure certainty.

The Importance of Talking to the Patient

As mentioned, history-taking is absolutely essential to proper diagnosis. Not only does it ensure a “general approach” to the patient, as outlined earlier, but it also obtains a wider matrix of information, the “prior probabilities” in which more correct, more efficient diagnosis can be made. There is a saying in medicine, perhaps not always adhered to, that the “history”, more than any blood tests or other fancy investigations, provides roughly “80%” of the diagnosis. Some say it accounts for even more.

Let me share a story. I worked for four and a half years at Samsung, at SAIT, the central corporate research lab, which also housed the CTO function for Samsung Electronics. Obviously, we had some of the world’s top scientists and engineers, and our focus was very much on technology. For a leading tech company like Samsung, technology is the mantra, the way, the be all and end all. So imagine the surprise when one of my technologically-oriented co-workers comes to me first thing in the morning, saying, “when I woke up I had this terrible, terrible, pain,” while pointing and rubbing the middle of his back on the right side. “What happened?!” I asked. “Did you fall down?” “Where you in a fight?” (these are obviously diagnostic questions

to rule out a traumatic etiology). He answered that he had gone to a company dinner the night before, drank a lot (my mind starts thinking “dehydration”) and he was awakened with this terrible pain, which he had never experienced before. And so this is what I told him, “I think you have a kidney stone, and you should go to the doctor to have that evaluating.” Even though I was fairly confident of the diagnosis (e.g. all the prior probabilities pointed to a highly positive outcome on an x-ray for kidney stone), the reason to go to the doctor would be to determine if it was large (e.g. > 5mm) or small (< 5mm) — again, “duality” — which would imply a different treatment approach.

Rather than thank me for my advice, my colleague looked at me with disbelieving eyes: “How do you know that? You didn’t do any tests? How do you know I have a kidney stone?” I answered that while confirmatory tests would be required, the history (he scoffed) strongly suggested that. The next day, after he returned, feeling much better, by the way, I asked him, “So what was the result?” He sheepishly looked down: “a kidney stone.” After that, he seemed convinced that I was some sort of magical “seer” who could somehow conjure up diagnosis from nothing. In reality, I was just applying the power of “talking to the patient”, taking a good history, which is often nearly all a doctor needs to establish the diagnosis. It’s actually one reason why we ourselves (and doctors themselves) are often the poorest diagnosticians when it comes to ourselves. Sometimes we are in our own denial and so we don’t take the right history, we don’t look generally enough, to get it right when it comes to our own illnesses.

Treatment: Is it Medical or is it Surgical?

Among the many dualities in medicine, one of the most fundamental is that of diseases being “medical” or “surgical”. There is a very profound difference between

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the two that is not just theoretical, not just practical, in terms of the care of the patient, but even pervades the entire structure of medicine and the healthcare industry. Roughly speaking, “medical” diseases are those that are generalized or “systemic” throughout the body and are treated by medicines, namely drugs, while “surgical” diseases are those that are localized or regional, and require some sort of intervention for their treatment. Many diseases can actually be both “medical” and “surgical” either at the same time or at different stages in their development. Early-stage cancer, for example, being localized is often treated surgically, with removal of the tumor, while late-stage cancer, with disseminated metastases throughout the body, may no longer be surgically treatable but rather requires chemotherapy.

In the case of the kidney stone example above, I mentioned that 5mm was the rough “cut-off” point for determining whether the disease was medical or surgical. Less than 5mm implies that the stone can likely be passed (usually quite painfully) through aggressive fluid therapy alone (e.g. medical treatment). Experience has shown that stones greater than 5mm are unlikely to spontaneously pass and thereby require some form of intervention, such as a catheter, stent, shock wave lithotripsy, or even “cutting” surgery, to remove.

So now you can think like a doctor: your colleague comes to you complaining of back pain. You ask general questions, to rule out a wide a wide spectrum of causes, you talk to the patient to find out more background, compiling these among “prior probabilities”, come up with the leading diagnosis of “kidney stone” and then think, “is this medical or is this surgical?” There’s obviously a lot more to how doctors think but these are a sampling of some of the core principles. You can find out more at the Seoul Mini-MD coming up on August 22nd at COEX (see: http://www.seoul-mini-md.

com/). The program will help you be a better health professional and, who knows, a little knowledge and understanding of doctors think may even save yours or one of your loved ones life one day?

About the Author

Ogan Gurel, MD, is the CEO / Founder, NovumWaves and former Visiting Professor, Samsung Advanced Institute of Science & Technology. He is anHonorary Fellow, University of Melbourne and an advisor to numerous healthcare startups and companies.

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