Basics for the Wards: Reading a Chest X Ray
Chest X-rays (aka CXR) are one of the most basic imaging studies done in medicine. Almost every hospitalized patient has one and you will see hundreds of them by the time you finish med school.
But it was be super easy to get distracted by the huge glaring pathology (like a giant mass) that you miss other pathology (like a broken clavicle). So, like with reading EKGs, it’s best to have an algorithm you run through for every CXR so you don’t miss anything.
Disclaimer: Again, this is just a general introduction with some basics to help you start out on wards. There is a lot more to interpreting chest x-rays that what I mention, that is why radiologists are awesome.
First: What is the view- is it AP (front to back) or PA (back to front)? Lateral CXRs are obvious.
If the patient is able to stand, a PA view is generally preferred. AP is generally when patients are confined to the bed- also you usually cannot diagnose cardiomegaly from an AP view because the heart is almost always bigger in this view. How do you tell the difference between them? Look at the scapula- in a PA view the scapula are usually clear of the lungs, whereas in an AP view the two generally overlap. Sometimes the clavicle positioning can be a good clue too- see the differences between the two?
Second- what is the quality, because that can have a major effect on your interpretation. A good mnemonic is RIP.
- Rotation - Measure the distance of each clavicle from the spinous processes at that level, if they are equidistant then the patient is not rotated.
- Inspiration - If you can count nine posterior ribs within the lung fields before you reach the diaphragm, then there was enough inspiratory effort. Poor inspiratory effort will look like the patient has an airspace disease.
Note: Posterior ribs = more apparent, look more horizontal. Anterior ribs = less visible, 45ish degree angle towards feet
- Penetration - With flawless penetration, you should be able to see the thoracic spine through the heart.
Underpenetration= Left hemidiaphragm and left lung base will not be visible, and pulmonary markings will appear more prominent than they actually are. Ahhhh!!!!
Overpenetration= what is even happening here
OK, now you’re ready to see what is going on with the patient. I suggest the systematic approach, which has the handy mnemonic ABCDE= airway, bones, cardiac, diaphragm, everything else (lungs). I’m not going to go into all the pathology associated with everything, because that would take forever.
- Airway: Is the trachea patent and midline? Can you see the mainstem bronchi and the carina? If there is an endotracheal tube in place, make sure that it is 3-4 cm above the carina. Also check to make sure the mediastinum is not deviated or abnormally wide.
- Bones: Is anything broken or dislocated? Any lytic lesions?
- Cardiac: How clear is the cardiac silhouette? Is the heart enlarged? What about all the vessels- the aorta, SVC, IVC, etc.
- Diaphragm: Is the right side higher than the left but not like wayyyy too much? Are the costophrenic angles clear (if not, could be an effusion!)?
- Everything else: NOW you can look at the lungs. Is there an infiltrate or a mass? What about pneumothorax? Also check for you friendly neighborhood gastric air bubble, it’s supposed to be below the diaphragm.
Easy enough, right? Good luck!