How to read a chest x-ray (step-by-step)

How To Read A Chest X-ray [Step-by-Step]

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Are you an aspiring radiologist who is new to the field, or a medical student who wishes to know how to read a chest x-ray? This article can help!

A chest x-ray is a standard radiology test that creates an image of the chest and internal organs. It is sometimes referred to as chest radiograph, CXR, or chest roentgenogram.

chest xray

It is needed when the patient is experiencing chest pain, shortness of breath, or chest injury. It also helps detect heart problems, pneumonia, cancer, collapsed lungs, and other conditions.

You can probably imagine how necessary a chest x-ray is in detecting several medical issues and conditions. It is why knowing how to interpret and read chest x-rays is a valuable skill to have in your arsenal, no matter what specialty you practice.

Scroll through my article to learn everything you will need to know about chest x-rays. Continue reading as I walk you through the ABCDEFG method and the step-by-step procedure!

What Is A Chest X-Ray?

A chest x-ray is a non-invasive radiology test that provides imaging of the heart, blood vessels, lungs, bones in the chest, spine, and airways. The chest will be briefly exposed to radiation from an x-ray machine for the test, producing an image on a digital computer or film.

If you have seen a chest x-ray image or film before, you would surely notice that it is always black and white. Only darkness and brightness are the defining features of various structures.

Each organ in the chest cavity soaks up varying degrees of radiation, leading to different shadows in the image.

For instance, the bones in your chest (vertebrae and ribs) tend to absorb more radiation, and thus appear whiter and brighter on film. Meanwhile, the lung tissue, mostly air, allows radiation to pass through, resulting in a darker shade in the image.

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Physicians ask for chest x-rays for various reasons. Some of the common medical conditions that are detected using chest x-rays are: 

  • Enlarged heart
  • Lung mass 
  • Pleural Effusion (fluid around the lung)
  • Congestive Heart Failure
  • Pneumonia
  • Rib fractures
  • Pneumothorax (air around the lung)
  • Aneurysm (ballooning of the aorta or another blood vessel)
  • Cancers or tumors
  • Pleuritis (inflammation of the lining of the lungs)
  • Calcification (hardening of the aorta or heart valve)

Other possible reasons why you will need a chest x-ray:

  • Before surgery or part of a physical exam
  • To check chest cavity and lungs after surgery  
  • To check and see if the disease is worsening
  • To check for symptoms related to the lung or heart
  • To inspect implanted pacemakers wires and other internal devices. 

doctor having operation

Risks Of Chest X-Ray

You should know by now that going through a chest x-ray means radiation exposure. It may sound worrying or concerning, but that is not always the case.

The amount of radiation a chest x-ray uses is low and minimal — even lower than the amount you are exposed to through natural sources in the environment.

It would be helpful to have a list of past x-rays and scans for health reasons. You can tie the number of x-rays you did in the past and the x-ray treatments you had over time to the potential risks of radiation exposure.

While the benefits outweigh the risk, you will be required to don a protective apron if you need several images. The risks are higher for pregnant women as it could lead to birth defects.

How To Prepare For A Chest X-Ray

The patient will wear a gown for the procedure. They also need to remove metal-containing materials such as jewelry before the x-ray. There will be no additional preparation (such as fasting) needed.

It is necessary for the patient to undress from the waist up as clothes can obscure the x-ray image.

Pregnant women will need to notify their healthcare providers about their condition to save the fetus from unnecessary radiation exposure. A protective lead that covers the abdomen will be required to avoid complications.

how to read a chest xray

What Happens During The Chest X-Ray? 

After wearing a gown and removing metal-containing materials, the body is positioned between a plate that creates the image and the machine that produces the x-rays. There might be an instance wherein the patient will be asked to move into various positions to take views from the side and front of the chest.

To obtain the frontal view, the patient will stand against the plate, hold their hands up or to the sides. Then, they need to roll their shoulders forward.

It would be best to ask the patient to take a deep breath and hold it in for a couple of seconds. Holding the breath while inhaling can help the lungs and heart show up more clearly on the image.

The patient will need to turn and place a shoulder on the plate to obtain the side view. Then, raise their hands over their head. Again, the patient will need to take a deep breath and hold it in.

The entire procedure is harmless and non-invasive. The patient would not feel any sensation since the radiation would pass through their body.

For those who have problems standing up, the test can be completed while seated or lying down.

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How To Read A Chest X-Ray

Chest x-ray reviews are a critical competency and skill for junior students, medical students, and other allied health professionals. It is a vital procedure that can detect various medical conditions. 

It is also worth noting that you will need extensive knowledge about anatomy to know what you are looking for. You can check out my article about the best resource for anatomy in medical school.

In reading and interpreting chest x-rays, it is crucial to know the step-by-step procedure.

     how to read a chest x-ray

Step #1: Confirm Details

You may begin the x-ray interpretation by double-checking the details. 

  • Patient details such as complete name and date of birth.
  • Date and time when the film or image was taken
  • Previous imaging (for comparison)

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Step #2. Assess Image Quality

The next thing to do is assess the quality of the image taken. For this, you may use the mnemonic ‘RIPE‘.

Rotation

Check if the x-ray hit your patient straight on. A straight x-ray is typical and the norm.

The medical aspect of each clavicle must be of equal distance from the spinous processes. The spinous processes must be vertical against the vertebral bodies.

Inspiration

How well did the patient breathe during the procedure? An adequate inspiratory effort allows the chest to expand, which translates to better visualization in film. The 9 pairs of ribs should be visible posteriorly to consider the x-ray adequate for inspiration.

Projection

Check if the film is AP (Anterior-Posterior) or PA (Posterior-Anterior). If the film has no label, you can assume it is a PA image as it is the preferred type of chest x-ray.

Also, if you do not see the scapulae projected within the chest, it is safe to assume it is a PA.

Posterior-Anterior:

 PA chest x-ray

www.physio-pedia.com

Anterior-Posterior:

   

www.physio-pedia.com

Exposure

Everything in the film must be clear and detailed. You should be able to identify or point out the costophrenic angles (places where the diaphragm meets the ribs) and lung apices (one of the four chest radiograph zones).

The vertebrae should be seen behind the heart, and the left hemidiaphragm should be visible to the spine. 

Normal chest x-ray:

Normal chest x ray and the different parts

www.ebmconsult.com

Step #3. Use the ABCDEFG Approach 

In reading and interpreting chest x-rays, the ABCDEFG mnemonic method is probably the best method to use. It provides a systematic approach that ensures you will not forget anything. 

A – Airway

‘A’ in the mnemonic stands for airway. This part is when you interpret the airway visible on the x-ray. 

airways - how to read a chest x-ray

www.radiologymasterclass.co.uk

  • Trachea

In assessing the chest x-ray, the trachea should either be slight to the right or smack in the center. If deviated, check whether it is because of the patient’s position or another pathological reason.

A tracheal deviation may be due to the pushing or pulling of the trachea. Pushing could lead to tension pneumothorax, while the latter could be associated with lobar collapse.

Make sure to inspect any lymphadenopathy or paratracheal masses. You will need to trace the trachea to the carina. See if it is straight and midline.

Also, you can further inspect to see if there is any narrowing. 

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  • Carina and Bronchi

The carina is located at the point where the trachea separates into the left and right main bronchus. The division should be reasonably visible on an appropriately exposed chest x-ray.

The right bronchus is shorter, wider, and more vertical than the left. The difference in orientation and size leads to more inhaled foreign objects being lodged on the right bronchus.

Trace down the main bronchi. See if the carina is wide (more than 100 degrees). Check if there is an inhaled foreign object and if there is bronchial cut-off or narrowing

hilar - how to read a chest x-ray

www.radiologymasterclass.co.uk

  • Hilar Structures

The hilar, on the other hand, consists of the major bronchi and main pulmonary vasculature. Each hilar has a series of lymph nodes that are not visible in healthy people.

The right hilum should be slightly lower than the left, but there is variability between persons. The hilar are typically the same size, which means asymmetry should warrant suspicion.

Several pathologies could cause hilar enlargement. The bilateral symmetrical enlargement could mainly be associated with sarcoidosis, while unilateral enlargement may be due to underlying malignancy. 

Abnormal positioning of the hilar could also be due to many reasons.

B – Breathing / Bones

After assessing the airway, move on to ‘B,’ which stands for Breathing or Bones. It is when you evaluate and interpret both the lungs, the pleura, and the bones.

normal lungs - how to read a chest x-ray

www.radiopaedia.org

  • Lungs

You may start by checking the lung borders. See if the lung markings are visualized out of the patient’s chest wall. 

Compare the zones between lungs. Take note of any asymmetry (though, some asymmetry is typical and could be due to various anatomical structures).

Increased airspace shadowing in a particular area of a lung field may mean pathologies, such as consolidation or malignant lesions.

If a pneumothorax is what you are specifically looking for, check if there is abnormal air collection between the parietal pleura and visceral.  

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  • Pleura

The pleura is not typically visible in healthy patients. If you notice it visible, it could mean that there is a presence of pleural thickening, which could be related to mesothelioma.

Check the lung borders to make sure that the lung markings extend to the edges of the lung fields. The absence of lung markings could indicate pneumothorax.

Blood (haemothorax) and fluid (hydrothorax) could accumulate in the pleura, leading to an increased opacity in a specific area of the chest x-ray. In some instances, a combination of fluid and air can build up in the pleura space (hydropneumothorax), eliciting a mixed pattern of decreased and increased opacity within the cavity of the pleura.   

Normal pleura:

normal pleura - how to read a chest x-ray

www.radiologymasterclass.co.uk

Pleural thickening:

pleural thickening - how to read a chest x-ray

www.researchgate.net

  • Bones

Assess the bones that are visible in the film, top to bottom. Check for fracture, subluxation, dislocation, and osteoblastic.

The bone edges must be smooth; otherwise, a fracture is possibly indicated. Also, assess the density of the bones, metastatic lesion, or oedema

Fracture of the ribs:

Fracture of the ribs - how to read a chest x-ray

www.researchgate.net

C – Cardiac

‘C’ stands for Cardiac/Cardiovascular. You will need to check the heart and the heart borders for this part. 

  • Heart

The heart should make up no more than 50% of the thoracic width in a healthy person. Though, this rule only applies to PA chest x-rays since AP films tend to exaggerate heart size.

If you notice the heart occupies more than 50% of the thoracic width in a PA film, then Cardiomegaly is possible. Cardiomegaly could potentially develop for various reasons, such as cardiomyopathy, valvular heart disease, and pulmonary hypertension. 

Normal heart size:

normal heart size

www.radiologymasterclass.co.uk

  • Heart Borders

The heart borders should be well defined in healthy patients. The right atrium makes up most of the right border, while the left ventricle makes up most of the left.

Reduced definition on the right border could potentially mean a right middle lobe consolidation. In contrast, a reduced definition on the left is usually related to lingular consolidation

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D – Diaphragm

The ‘D’ in the mnemonic is the diaphragm. 

normal diaphragm

www.radiologymasterclass.co.uk

  • Diaphragm

The right diaphragm, in typical cases, is higher than the left due to the liver. 

If you see the presence of free gas under the diaphragm, seek an urgent senior review since further imaging (CT abdomen) is likely needed to identify the source of the free gas. 

Though, beware of the false impression of free gas under the diaphragm, called the pseudo-pneumoperitoneum, including the Chilaiditi Syndrome. 

This syndrome consists of abnormal positioning of the colon between the liver and diaphragm, which results in an appearance similar to free gas. Do not be misled!

It is possible due to the bowel wall and diaphragm becoming indistinguishable because of their proximity. If you are a junior doctor, always consult with a senior colleague to discuss the scans. 

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  • Costophrenic Angles

These angles are formed from the dome of the hemidiaphragm and lateral chest wall. In a healthy person, the costophrenic angles should be visible on the chest x-ray as a defined acute angle.

Costophrenic blunting is what you call the loss of this acute angle. It indicates the presence of fluid in the area. 

Left costophrenic angle blunting (A) and improved condition (B):

left costophrenic angle blunting and improved condition

www.researchgate.net

E – Effusion

Next is ‘E,’ which means Effusion.

Pleural effusions could be significant and blatant or small and subtle. You will need to inspect the costophrenic angles for any sharpness and blunted angles, the latter indicating small effusions. 

Identify major fissures. If they are more profound than usual, it could mean that fluid is tracking along the fissure.

Inspect the lateral film and look out for small posterior effusions.

Malignant pleural effusion:


malignant pleural effusion

www.radiopaedia.org

F – Fields / Fissures / Foreign Objects

You must check for infiltrates. If you spot any, identify the location by using known radiological phenomena (e.g. loss of the contour of the diaphragm or borders of the heart).

Keep in mind that the right middle lobe adjoins the heart while the right lower lobe does not. The lingula, on the other hand, abuts the heart’s left side.

Identify the pattern of the infiltrates — alveolar pattern (nodular or patchy) versus interstitial pattern (or reticular).

You also need to look out for masses, pneumothoraces, vascular markings, and consolidation in the lungs. The vessels should taper, and they should also be almost invisible in the left periphery.

Inspect both major and minor fissures for fluid, thickening, or change in position. Lastly, check out the positions of foreign objects (pacemaker leads, ETT, central venous lines, NGT, and more).

Infiltrate in the right lung:

infiltrate in the right lung

www.researchgate.net

G – Gastric Air Bubble / Great Vessels

The last letter stands for Gastric Air Bubble and Great vessels. You must check the aorta’s shape and size, as well as the outlines of the pulmonary vessels. The aorta knob needs to be visible.

You should be able to see the gastric bubble. It should not be displaced. 

You must beware of hiatus hernia and look for free air. Check for bowel loops between the liver and diaphragm. 

Gastric bubble in the chest:

gastric bubble in the chest

www.researchgate.net

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There is no one strict way or recommended analysis methodology in reading chest x-rays. It does help if you read them systematically using the ABCDEFG approach to reduce the chances of missing a diagnosis. 

Whether you choose to read the x-ray in an anatomical order or use a mnemonic is all up to you.

I would like to give credit to Physiopedia, Radiology Masterclass, Radiopaedia, EBM Consult, and ResearchGate, for they have served as references for this blog post.

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