Reading a chest X-ray

Definitions & Key takeaways

A chest X-ray is a diagnostic test that uses some amount of radiation to produce images of the structures inside the chest including the lungs, heart, and blood vessels. To read a chest X-ray, you can use an easy-to-remember checklist, which is associated with the first 7 letters of the alphabet: ABCDEFG. A is for the assessment of data and quality as well as looking for air where it should not be. B is for bones and the body wall, specifically looking for fractures, deformities, missing bones, and if any swelling, or masses are present. C is for the cardiac silhouette and its size. D is for diaphragms, which should appear fairly symmetric. E is for equipment, such as the lines, tubes, and wires involved in life support, and pleural effusion, a form of pathology commonly seen on X-rays. F is for lung fields which should look symmetric, without any haziness, white dots, or blotches. Finally, there is G, which is for great vessels including the superior and inferior vena cavas, the ascending aorta, the aortic arch, the descending aorta, and the pulmonary artery.

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You can think of X-rays as high-energy photos that penetrate the body tissues so that we can see what’s going on inside.
Just like visible light, X-rays are less likely to penetrate denser materials. Conventional x-rays that show white bones on a black background are like photographic negatives.
The darkest parts of the film like the lungs are areas where more photons can penetrate the body. In contrast, the sharp, bright white areas are where the dense bone material blocks photons from getting through.
Let’s go through this chest X-ray using an easy-to-remember checklist - associated with the first 7 letters of the alphabet: ABCDEFG.A stands for Assessment.
To avoid errors and wasted time, you should always begin by assessing the patient and exam data. You want to verify the patient’s data with the exam data (medical record number, date of the exam, etc.)
to ensure that you are looking at the right study and patient.You also need to assess image quality, because this will impact the accuracy of the test in detecting pathology.
For example, to ensure there isn’t excess rotation of the patient, you should make sure that the medial ends of the spinous processes are equally distant from the border of the vertebral bodies.
Rotation throws off the usual X-ray anatomy and introduces unwanted variation. Next, a good inspiration film should show at least the 10th or 11th posterior ribs.If the lungs are not fully expanded, we might miss important diseases.
Finally, we need to make sure that the exposure isn’t too bright or too dark. To check for this, you can look for fine markings in the lung fields to make sure they are visible.
If the fine lung markings aren’t visible, then the X-ray may fail to detect some diseases. A also reminds us to make sure there isn’t “Air where it shouldn’t be.” Finding air where it should not be - or more commonly “ruling it out” - remains one of the most important uses of medical X-rays.
Diagnoses like pneumothorax, pneumomediastinum, pneumoperitoneum, and subcutaneous emphysema are all examples of “air where it shouldn’t be.” All of these are surgical emergencies and can be diagnosed by a simple chest X-ray.
Finally, if the major airways like the trachea are bent or deviated, (Another example of air where it shouldn’t be), may signal an underlying mass.B is for bones.
Start by looking at both clavicles and all 12 pairs of ribs one at a time to make sure that there are no fractures, deformities, or missing bones.
B is also for the body wall and soft tissues outside of the chest. This is an easily overlooked part of the chest x-ray, and it should be checked for swelling, masses, etc.C is for cardiac silhouette and size.
This is the cardiac silhouette and there’s the atrial appendage, the right atrium, and the left ventricle. Measuring across a normal heart is less than 50% of the greatest diameter of the rib cage measured from the inner portion of each rib - any larger, and there may be cardiac pathology.
D is for the diaphragms, which shouldn’t be too flat, but appear fairly symmetric. You can assess flatness on the lateral view by estimating that the hemidiaphragm is 1.5 cm above the line connecting the costophrenic angle posteriorly and sternophrenic angle anteriorly.
E is for equipment, such as the lines, tubes, and wires involved in life support. It’s important to note exactly where they’re located relative to other structures and whether they’re in “functional position.” For example - an endotracheal tube should be in the middle of the trachea and its tip should be more than 2 cm from the tracheal bifurcation, or that a nasogastric tube should have its tip well within the stomach.
E is also a reminder to check for a pleural effusion, which is a common but subtle form of pathology that you can see on an X-ray.
Pleural effusions are fluid that collects at the costophrenic angle and causes blunting of the normally sharp costophrenic angle.
F is for lung Fields, which should look symmetric. There shouldn’t be any haziness, white dots, or blotches.
While looking at lung fields, having a frontal and a lateral X-ray allows us to determine lobe and lung of which an abnormality is located.
In this case, a nodular mass is visible in the inferior, lateral, and anterior left lung. Meaning it’s most likely within the anteromedial basal subsegment of the left lower lobe.
This can be confirmed with a chest CT.Lastly, G is for great vessels, which includes the superior vena cava, inferior vena cava, ascending aorta, aortic arch, pulmonary artery, and descending aorta.
You want to make sure any of these structures is in the right location and is the right size. On the left side of the heart, the aortic knob should be the highest up, followed by the pulmonary trunk and left atrium.
On the right side, the superior vena cava, ascending aorta, right atrium, right ventricle, and IVC should all be visible.
Deviation may be the result of congenital abnormality or disease. Okay - to recap using ABCDEFG.
A is for assessment of data and quality as well as looking for “air where it should not be.” B is for bones and the body wall.
C is for cardiac silhouette and size. D is for diaphragms.
E is for equipment and effusions. F is for lung fields, and G is for great vessels.
inferior. Vena cava should all be visible deviation.
May be the result of congenital abnormality or disease. Okay, to recap using a b, c, d, e, f g is for the assessment of data and quality as well as looking for are where it should not be.
B is for bones in the body. Wall C is for cardiac silhouette in size d, is for diaphragms.
He is for equipment and effusions. F is for lung fields.
In G is for great