Chest X-ray interpretation: Clinical sciences

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Chest radiograph, or chest X-ray, is one of the most commonly performed imaging studies, and can provide a large amount of useful information.
So understanding how to approach and interpret a chest X-ray is an incredibly important clinical skill.So the most common indications for a chest X-ray include chest pain, shortness of breath, or cough.
It is also often used as a part of trauma and preoperative evaluation, and after placement of monitoring and support devices.
While there are no absolute contraindications for a chest X-ray, and the radiation dose is small, you do want to ensure it is truly necessary, especially if your patient is pregnant.Now, let’s discuss a systematic approach to interpreting a chest X-ray.
This is going to involve checking the patient and study details, then assessing the quality of the study. Next, you want to scan the chest X-ray systematically and completely.
You are looking to identify any abnormalities. Finally, you want to get a radiologist’s review of the film.
Let’s go through each of these steps in more detail.The first step in interpreting a chest X-ray is to check the name and date of birth on the image to confirm it’s the right patient, and the date and time to confirm it’s the right study.Once you’ve done that, you are going to assess the quality of the chest X-ray.
You’ll look at six main factors: projection, orientation, rotation, angulation, penetration, and inspiration. Remember, a good quality image gives you a lot of information, and a bad quality image could cause you to misinterpret findings.
Begin with projection. Look to see how the film was taken.
Is it a PA, or posterior to anterior, AP, or anterior to posterior, or a lateral study? The standard chest x-ray is PA.
However, AP films are often seen when the patient needs a portable machine, like when they’re bedbound. Lateral films can be obtained with both.Next, look at the orientation of the chest X-ray.
Check the left and right markings. You’ll see a “L” or left marker on the right side of the image.
Also the position of the patient is important. Supine means they’re laying down facing upward; lateral is when they’re laying on their side; semi upright is when their upper body is elevated 45 to 60 degrees from the bed; and upright is when they are sitting up at 90 degrees.You then need to assess whether the patient is rotated toward their left or right.
To do this, look at the relationship between the clavicles and the spine. If the medial ends of the clavicles are equidistant from the thoracic spinous process, the patient is not rotated.Next, assess angulation, which is the angle that the X-ray penetrates the body.
The clavicle should lay over the third rib, and only a small amount of the lung’s apex should be visible above the clavicle on a standard chest X-ray.
Too little lung tissue and the shot is taken from below, means it’s angled upwards; while too much and the shot is taken from above, means it’s angled downwards.Penetration is also very important.
If a film is underpenetrated or overpenetrated, you may not be able to visualize important pathology. If the study is adequately penetrated, you should see the thoracic spine through the lower cardiac shadow.The last quality metric you want to look at is inspiration.
You should see eight to ten posterior ribs above the diaphragm. With poor inspiratory effort, you’ll see less than eight ribs, and may mistakenly think the resulting crowded lung markings represent a pathology.Now, if your evaluation indicates a poor quality chest X-ray, you need to interpret it very cautiously.
You can also repeat the study if needed.Once you’ve assessed the quality of the chest X-ray, you are ready to “read” it.
You want to scan the study systematically and completely. There are many methods to read a chest X-ray, but the important part is picking a system and using it consistently.
This way, you will evaluate all structures and avoid skipping findings. For each chest X-ray, you must evaluate the mediastinum, hilum, trachea, lungs and pleura, diaphragm, bones and soft tissues, abdomen, as well as foreign bodies like support and monitoring devices.As you systematically review the chest X-ray, you should identify any abnormalities and formulate a differential diagnosis for those abnormalities.
If a previous chest X-ray is available, pull it up and compare findings. Also remember that radiological findings aren’t diagnostic, but they can help guide a differential diagnosis when correlated to the patient’s clinical picture.
For instance, a pulmonary infiltrate in a patient with a fever can indicate pneumonia, while in a trauma case, it can indicate a pulmonary contusion.While personally interpreting the chest X-ray is critical, you should also obtain a radiologist’s review of the study.
Review the film with a radiologist, or look at the radiologist’s report once available.Now, let’s look at how to evaluate important structures, and some abnormalities that you may see on a chest X-ray.
For the mediastinum, it’s important to observe the overall width, and examine the contours of the heart and aorta.A widened mediastinum, meaning wider than six to eight centimeters, has many potential causes.
These include aortic dissection, aortic aneurysm, or mediastinal mass. Basically, any pathology that causes an enlarged radiopaque mass in the mediastinum can show up as a widened mediastinum.Enlargement of the cardiac silhouette may indicate a pathology of the heart tissue itself, like when there’s cardiomegaly, or when there’s pathology affecting the pericardium such as pericardial effusion.You should also evaluate for pneumomediastinum, where there is a linear lucency outlining mediastinal structures.
This can be caused by alveolar rupture, esophageal rupture, or other etiologies where an air containing structure in the mediastinum ruptures.For the hilum, you want to compare the shape and density of the hila.
They should be concave and look similar to each other. Unilateral or bilateral hilar enlargement due to lymphadenopathy may indicate malignancy or infection.
Bilateral hilar enlargement may also be seen in pulmonary hypertension where the pulmonary vessels are dilated.Next, let’s talk about the trachea.
You want to look at its size and course. You may see tracheal narrowing, also known as tracheal stenosis.
The trachea may also appear “crooked” if it’s displaced by a mass.Sometimes, the entire trachea is deviated toward one side.
This can be seen with a tension pneumothorax, where the trachea deviates away from the affected lung. You can also see it with severe atelectasis, where the trachea is “pulled” toward the affected lung.When evaluating the lungs and pleura on a chest X-ray, there are a few things to look for.
You want to assess if lung markings extend to the end of the lung field. If you see a visceral pleural line with the absence of distal lung markings, that indicates a pneumothorax.You also want to look for any localized abnormal opacity, such as opaque masses or consolidation, as well as diffuse opacity.
Infections and malignancy should always be considered when you see localized abnormal opacity in the lungs; while diffuse opacity in the interstitium can be due to pulmonary edema, which is frequently seen in heart failure.Let’s talk about the diaphragm next.
Normally, the right hemidiaphragm should be higher than the left, since the liver is located right below. A marked elevation in a hemidiaphragm may indicate a paralysis of that diaphragm.You should also evaluate the costophrenic angle.
If this is blunted rather than sharp, it could indicate a pleural effusion where fluid builds up in the pleural space, and accumulates in the costophrenic sulcus when a patient is upright.It’s also important to look at the bones and soft tissues.
Carefully assess the bones for fractures, including the ribs forming the chest wall, as well as the clavicles, vertebrae, the humeral head and scapulae.You also want to look for subcutaneous emphysema under the skin and soft tissue of the chest wall.
This can be seen as gas within the chest wall. This could be related to the presence of a pneumothorax or pneumomediastinum.The upper portion of the abdomen is also captured in a chest X-ray, and it is important to assess this area, as well.
Look for pneumoperitoneum, or free air under the diaphragm. This could indicate a bowel perforation.
You may also see dilated loops of bowel, which could suggest a bowel obstruction. In patients with diaphragmatic rupture, you may see abdominal organs like the stomach herniating into the chest cavity.Many foreign bodies can be seen on a chest X-ray.
This includes swallowed or inhaled objects that are radiopaque or support and monitoring devices. So a chest X-ray may be used to assess the proper placement of devices like endotracheal tubes, central venous catheters, nasogastric tubes, and more.
It is important to look for these support and monitoring devices, and ensure their continued proper placement, when evaluating a chest X-ray.Alright, as a quick recap… Chest X-rays are a common imaging study, and can provide a lot of useful information.
You should have a systematic approach to interpreting a chest X-ray. First, check the patient and study details.
Then assess the quality of the study. After that, read the chest X-ray.
Be systematic and read it the same way every time. You’ll be less likely to miss something if you do.
Identify any abnormalities, and interpret them in the context of the patient’s previous images and clinical picture. You should also obtain a radiologist’s review of the study, by reviewing the film with them or reading their report.