You can't actually earn your M.D. in a quarter of an hour, but this crash course can teach you how to think like a doctor. In some cases, that could be enough to save your life
"Gunners" was what we called them, with a mixture of respect and contempt that none of us really tried to sort out. They were the ones who just couldn't give up, even after being accepted into medical school, on what was clearly a lifelong campaign to be the Smartest Kid in the Room. All our grades were pass-fail and no class ranks were at stake, but still the gunners spent the first 2 years leaning forward in the front row, elbows cocked, ready to raise their hands at the first question the lecturer let fly.
In the midst of medical school's unassimilable flood of information, when no one knew which fact, if any, was going to be the one that saved somebody's life, it was difficult not to view such compulsive self-confidence without a little envy.
Until the third year. That's when the scene shifted from the lecture hall to the hospital wards. I still remember the day the rules changed. I was one of two students on the pulmonology service. The other student was a notorious gunner; already determined to become a neurosurgeon, he had an aura of polished chrome. He had just finished a dazzling presentation of a new patient, a 65-year-old man with bad kidneys and an atypical pneumonia who had apparently spent the night on the verge of respiratory failure.
"And what do you think we should do now?" the attending asked.
"Bronch him," the gunner shot back, suggesting a standard test beloved by pulmonologists, which involves inserting a rigid bronchoscope into the patient's lungs to bring up pictures, tissue samples, and usually a diagnosis.
"Really?" the attending replied mildly. "Aren't there less expensive ways to kill him?"
The gunner backpedaled, stammering, "CT him, then?"
"Cheaper," the attending agreed. "Until you factor in the dialysis."
Then he cracked a weary smile. "You know what's going to happen if you keep shooting from the hip, don't you, son?"
"What?" the gunner asked warily.
"One of these days you're liable to hurt somebody."
Doctors don't think like gunners. As the producers of House know, doctors actually think more like Sherlock Holmes. (This is not surprising, given that Holmes's creator, Dr. Arthur Conan Doyle, modeled the fictional detective after one of his medical school professors.) "You know my methods, Watson," Holmes says. "When you have eliminated the impossible, whatever remains, however improbable, must be the truth." This slow, painstaking method of unlocking diagnostic puzzles is dictated by the bizarre complexity of human physiology and illness.
So doctors learn to avoid leaping from fragmentary evidence to the most likely answer. They're trained instead to hold off answering at all for as long as possible. We "sift the differential"—that is, we construct a list of all possible explanations of the patient's symptoms, rank them in order of deadliest or most common (or both), and then collect the evidence necessary to rule out every item on that list until, as Holmes explains, whatever remains must be the truth.
All medical questions begin not with obscure facts about physiology or disease but with a set of symptoms. The medical workup is based on things you can feel, touch, see (and sometimes smell): a headache, a sore throat, a pain in your ankle. If you take that as your starting point, and bear in mind that the object of the game isn't to jump to a conclusion but to weed out all the wrong answers, diagnosis becomes (slightly) less mysterious.
Some doctors grow nervous when they think a patient is diagnosing himself. Doing that can definitely cause trouble, and the Internet has made it easier than ever for you to get in over your head. But some doctors also believe that certain taciturn populations—I'm talking about men—might be more willing to seek help if they can find basic information online before they have to ask a human being for directions. And these days, when more and more nonmedical concerns interfere with medical decision making, and when you can find yourself looking at serious financial hurt for that unnecessary trip to the emergency room, you may understandably feel that you need some way of knowing when to seek help. Of course, medical professionals are your best resources for making that call. But there's no escaping the reality that we are all, ultimately, our own first responders. That decision to pick up the phone isn't going to come from your doctor: It has to come from you.
Take the humble bellyache. It's a simple thing to recognize—you know it intimately. But the differential diagnosis of abdominal pain is so big that you have to break it down by regions of the belly. And even within those subsets are dozens of possible diagnoses, from acute intermittent porphyria (an inherited metabolic disorder) to polyarteritis nodosa (an arterial inflammation) to mesenteric ischemia (blockage of one of the arteries supplying your gut with blood). Or it could be something as benign as gastroenteritis—a stomach bug.
This is where the art begins, by doing whatever you can to shorten the list. You set up a differential that—you hope—is manageable, and then you begin sifting.
Consider the following cases as a way to get a feel for the way your doctor thinks. All the scenarios are hypothetical, and you shouldn't mistake any of them for medical advice that could apply to any particular situation you might face. But try them on and see what it's like to work through the differential—it's how your doctor turns ordinary worrying into an art.
Sore Throat, Cough, Runny and/or Stuffy Nose
It's the common cold, right? Gunner. Even here there are other possibilities to consider.
If you don't have nasal congestion, if the cough is dry, if you have a fever above 101°F, if the illness came on suddenly and now you feel like a truck hit you, it could also be influenza—historically the world's deadliest virus, by body count. If that's the case and you're in ordinary good health, your doctor might send you on your way with the reassurance that you'll probably be okay.
But if you have heart or lung disease or diabetes, or any condition that impairs your immune system, you should let your doctor decide if you need a neuraminidase inhibitor—an antiviral medicine that can shorten a bout of influenza by a day or so. And no matter how healthy you are, if you have the flu and then find yourself becoming short of breath with minimal exertion, or if you start coughing up nasty junk, or if a few days into the illness the fever comes back and you experience shaking chills, seek help. You're developing pneumonia. A call to your doctor could keep you out of the hospital. Or save your life.
Headache
Headaches come in a bewildering variety, from the dull, all-over ache, to the blinding bass beat perched just above one ear, to that red-hot spike being driven past your eyeball. Some come with visual hallucinations, odd imaginary smells, vertigo, vomiting, or a profound aversion to bright light and conversation. And some aren't headaches at all.
Tension headaches and migraines can usually be distinguished by location: A migraine tends to hit one side of the head, while a tension headache is more diffuse. A migraine is usually marked by an exquisite sensitivity to sound and light, putting its victim out of action for several days. A tension headache isn't usually disabling, and it typically fades overnight. Both of these are distinctly different from the much rarer cluster headache: an excruciating attack that explodes behind one eye, reaches a crescendo after about an hour, and then vanishes—only to return in a day or so. These come in salvos for a few weeks, and then disappear.
What all three have in common, however, is that they're "benign." Touch base with your doctor, who will probably reassure you (once it's clear that nothing serious is afoot) that nobody ever died from a headache. No matter how seriously they wished for the end to come.
But not every aching head is a headache. There are times when that throbbing skull really is a sign of something seriously askew. Watch out for...
The thunderclap headache
If it hits you like a bolt out of nowhere, intensifying in a few minutes into the worst headache you've ever had, call 911. The list of causes for this kind of headache isn't long, but almost everything on it can be very quickly fatal.
The sex/exercise headache
A headache that comes on quickly and furiously with violent physical exertion, or at the moment of orgasm, needs to be worked up. Most are benign; some are subarachnoid hemorrhages.
The headache that spreads to your neck
Benign headaches stay in your head. Headaches that don't can be meningitis or a hemorrhage. So yes, call 911, especially if you have a fever, if you're just getting over a bacterial infection, if you have a rash, or if you can't think clearly.
The headache that won't end
A headache that comes and goes for days, with a low-grade fever, visual disturbances, and aching in one or both of your temples, often signals an inflammation of the arteries that can leave you blind if not treated. See your doctor today.
The contagious headache
Your family is all home on a cold, rainy Saturday. As the day goes on you develop a headache that grows steadily worse. If anyone else has the same headache, move everyone outdoors immediately: There's a malfunction in your heating system and it's spewing carbon monoxide. Once you're out of the house, call the fire department—they'll know what to do. Your headache should clear up in a few hours.
The headache that's been worsening for weeks, wakes you up, and is there in the a.m.
This is the classic pattern for a slowly expanding mass. It may not warrant a 911 call, but I wouldn't let the sun go down without an MRI.
Breathlessness
Let's say you're a healthy 38-year-old man with no significant medical history who wakes up in the middle of the night feeling short of breath. You haven't been exposed to any respiratory illnesses. You're not coughing or feverish. Since you returned home from a business trip 2 days ago, you've been too tired to do much more than sit at your desk at work and in front of the TV at home. But now you're feeling distinctly...short...of...breath. Sitting up makes it a little better. But as you lie back down and wait for the sensation to go away, it doesn't. You try to draw a deep breath, but that gives you nothing more than a sharp twinge low in your chest. Your mouth is dry; your pulse feels fast. You've never felt anything like this before, and it's terrifying.
It should be. Part of that terror comes from a deep reflex. A neural loop connects your lungs with the part of your brain that experiences fear—and when we can't breathe, we're wired to panic.
The other reason to worry lies in the differential, which is the usual collection of the ugly versus the unlikely. It includes a collapsed lung, heart attack, and panic attack. In this hypothetical example—and ideally in reality—you don't have emphysema, sickle-cell anemia, or cystic fibrosis, and you haven't sustained a recent serious trauma to your chest, so we can rule out a collapsed lung, broken ribs, acute chest syndrome, pulmonary contusion, and flail chest. Since you're a reader of this magazine, I'll assume you're not a smoker, so an exacerbation of chronic obstructive lung disease isn't likely. You're not coughing up blood (right?), so massive hemoptysis probably isn't your problem either. Unless you regularly neglect to read warning labels, you probably haven't been exposed to toxic inhalants, insecticides, or chemical fires, so acute respiratory distress syndrome and organophosphate toxicity are off the list. You're not wheezing, and you don't make any odd noises when you inhale, so asthma and upper airway obstruction are out, too.
Which is all admirable, in a med-school gunner sort of way, but you're still short of breath. What's left on the list? Only 14 different possibilities, from heart attack to panic attack.
Of these, about half could be fatal by sunrise. Some of the others, such as panic, could result in a battle over coverage when you file the ER bill with your insurance company. But if you think the ER is expensive, try the funeral home. It's the only place I know where breathing isn't required. Pick up the phone and dial 911.
Light-Headedness
If you've ever experienced it, you never forget it: that horrible sensation of nausea, clammy cold sweat, and then consciousness sliding from your grasp as you settle toward the floor. The ER shorthand for this is "DFO," for "I done fell out." Your grandmother called it fainting; the preferred medical term is "syncope."
Syncope sends a lot of people to the emergency room. Most episodes are benign, caused by either simple dehydration ("orthostatic" syncope) or something called a "vasovagal reflex." In the latter case, some noxious trigger, usually in an internal organ, stimulates your vagus nerve, which signals your heart to slow down, your skin to break out in a clammy sweat, and your blood pressure to plummet. So if you're developing gastroenteritis from some bad sushi, your writhing gut can generate a reflex reaction that makes you faint. Vasovagal faints also happen to susceptible people when they go to the bathroom, when they stand too long, or when they've been startled.
Some other causes of syncope are less innocuous. For starters, cardiac arrhythmias can cause you to lose consciousness. Because arrhythmias are both potentially deadly and preventable, any DFO, unless it's part of a well-established pattern already diagnosed by your doctor, needs to undergo diagnostic study in the emergency room.
Finally, a relatively common genetic condition known as hypertrophic cardiomyopathy (HCM) can cause athletic young men to faint during exercise, and sometimes to drop dead. If you feel light-headed when you stand up, and if you easily become short of breath either when you lie down or suddenly in the middle of the night, make the trip to your doctor. You should do this especially if any of your close relatives died suddenly and inexplicably at an early age. HCM runs in families, and the majority of people carrying these genes don't know it.
The frustrating thing about fainting spells is that the most common result of the hospital workup is...nothing. Often it's impossible, after the fact, to pinpoint a cause. This is also the good news, because the causes that leave clear traces are things you don't want to have.
Spots
Rashes are common. Most are benign. Sometimes they're the first sign of disaster.
Rashes are also notoriously mysterious. Almost anything can cause them. I have seen rashes caused by exercise, riding a motorcycle, and eating red meat. Some people break out in hives whenever they become excited or embarrassed, a response guaranteed to destroy social lives.
But by far the most common rash is the blotchy red of contact dermatitis: It's itchy, unsightly, and rarely serious, usually caused by switching to a new laundry detergent, wearing a new item of jewelry, or trying on that shirt made of recycled mystery fibers that your sister gave you for Earth Day.
Some other rashes—including the annoying ones, like poison ivy, ringworm, yeast—can be hard to tell apart once you've tried to treat them with the wrong over-the-counter creams. The steroid that's good for poison ivy, for instance, won't cure yeast; it will, however, change it into a diffuse, red flush indistinguishable from contact dermatitis. And a rash that starts out as athlete's foot will sometimes become a diffuse red flush, except this one is hot and painful. Your locker-room leprosy has graduated from the merely annoying to cellulitis, a bacterial infection that gained a foothold through the cracked skin between your toes. That's a same-day doctor visit, unless you have diabetes, in which case you should go straight to an emergency room.
A painful, hot, sunburn-like rash that comes and goes, especially in somebody with a fever who recently had surgery (or any kind of wound, or even an ordinary IV catheter inserted), can be the warning sign of toxic shock syndrome, a scenario in which common skin bacteria like staph and strep enter your bloodstream, producing toxins that lead within hours to shock and organ failure. A rash accompanied by fever, headache, and joint pain can also be the first sign of meningitis or Rocky Mountain spotted fever, both readily fatal. Any rash that doesn't fade when you press on it needs immediate attention: You could be about to bleed to death due to any number of causes, from an autoimmune attack on your blood platelets to a hidden cancer.
There are hundreds more types of rashes lurking out there. This list offers just a sampling of some of the more common and dangerous ones. Your doctor may not recognize them all, but will know a dermatologist who can.
Lumps
Usually these are enlarged lymph nodes, swollen because cells in your immune system are busy getting their game on. Swollen nodes in your neck, armpits, or groin generally suggest infection nearby, or allergies. Big, tender nodes, typically in your neck and accompanied by a wicked sore throat, are mononucleosis until proven otherwise. There's not much you can do with mono (except spread it around), but someone with an active case is at risk of a ruptured spleen, so take your nodes to your doctor for a quick confirmatory test, lay off the contact sports, and wash your hands.
One of the worst things I ever saw in a clinic was when this big, awkward college student, a really nice guy, came in because his girlfriend had had mono and now he had these big swollen nodes and a low-grade fever. His girlfriend was afraid that if he played rugby that weekend he could rupture his spleen. The problem was that he didn't have a sore throat. What he did have was lymphoma.
Other items in the differential for lumps with fever include HIV, tuberculosis, and lupus. In case you have any doubts, lumps in your testicles are never normal. Lumps overlying your pectoral muscles also need to be checked, because guess what? Guys develop breast cancer too. And an isolated swollen lymph node that doesn't go down in a week or two, especially if it feels firm and immobile, must be biopsied for cancer.
Vision Changes
I once had a patient who'd been admitted to the ER for a brief dizzy spell. They'd given him fluid and he felt fine. When I checked him, he said, "Just one thing, doc: Why am I seeing two of you?" This was the first sign of the stroke that over the next 12 hours slowly paralyzed him.
New-onset double vision can signal a stroke, a blowout fracture of your eye socket, multiple sclerosis, or myasthenia gravis (an autoimmune condition in which your muscles become so weak you can wind up unable to breathe). Any time your vision suddenly changes in any way, whether it's parts of your visual field going dark (stroke), showers of floaters (detached retina), or generalized blurriness (imminent diabetic coma), you could be having serious problems not only in your eyes but elsewhere, ranging from autoimmune diseases of the circulatory system to HIV. I've also seen sudden changes in vision diagnosed by head CT (ordered usually after the patient has a seizure in the ER): The scan shows the telltale spots of pork tapeworm larvae in the brain.
Your eyes are attached directly to your brain. If you ever think they're trying to tell you something, listen.
Concussion
"Concussion" is the technical term for what happens when you're hit on the head hard enough to rattle the contents. We used to think that loss of consciousness defined concussion. We know now that even if you're not hit hard enough to be knocked out cold, a blow to the head can still shred the wiring in your brain. After the initial disorientation clears, you can develop headache, vertigo, nausea, and vomiting. Then come mood swings, insomnia, and/or memory loss. It's hard to talk. Bright lights and loud noises can be intolerable. You drop things, including your train of thought. This is the most mild form of brain injury.
Not all concussions are mild. Some are fatal, or inflict permanent brain damage. In the first minutes after the injury, symptoms of a serious concussion can be impossible to tell from those of a mild one; by the time severe symptoms appear, permanent brain injury may have already occurred. If you're hit on the head hard enough to make you even momentarily groggy, seek treatment immediately. And no matter what your coach or teammates (or that stupid little voice we all have in our heads) says, don't ever go back into the game. There's too much evidence that a second mild concussion too soon after the first one can add up to a lifetime of disability.
Once you've made it to the hospital emergency room, there's the controversial question of when you can turn around and go home. Even doctors disagree on this, but a few consensus guidelines are clear. The American College of Emergency Physicians recommends that a patient be sent home without additional testing only if he or she...
is alert, oriented, and able to follow simple commands;
has no suggestion of skull fracture (which can include some subtle signs, such as bruising around the eyes or behind the ears, blood behind the eardrums, or clear fluid leaking from the nose or ears);
isn't taking aspirin or other anticoagulants;
hasn't had a seizure;
can remember events up to 30 minutes before the injury;
has no sensory changes or weakness;
is younger than 65.
Even when you pass these tests, if the injury was from a car wreck, if you fell from higher than 3 feet off the ground, if you were drunk, or if you vomited more than once after the injury, then you've at least bought yourself a head CT. If the CT is normal and there's somebody at home to keep an eye on you (which means waking you up every 2 hours for a brief round of "what's your name?" and "who's the president?"), your doctor may let you go home as long as you're alert and oriented, and not bleeding or having a seizure.
Life is short. Art is long. When Hippocrates said this about the art of medicine, what he left out is that medical school is longer than any artistic performance I've ever sat through, but still much too short to cover everything you need to know. As with rashes, what you've read here just scratches the surface.
But even the art of medicine isn't concerned only with facts. There's also style—that Holmesian process of reasoning backward from all the possible causes to that one remaining truth. To form a reliable diagnosis, you still have to go to school. But style is something you don't need school to learn. To make the good decisions that will prompt you to go to your doctor so he or she can make the call, you don't need an M.D. But it might help to think like one.
The identifying characteristics of patients described in this essay have been altered to protect patient privacy. Any resemblance between such descriptions and any specific individual, living or dead, is a coincidence.
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