How to systematically read, review and assess lung x-ray?

Lung x-ray allows visualization of the structure of the lungs. It is commonly referred to as chest x-ray and is frequently used to assess lung related pathologies. In order to spot the pathological features or abnormalities, a clear understanding of the normal appearance of the organs and structures, including their size, shape and location, is imperative. A systematic approach that involves systematic reading, review and assessment of the chest x-ray image is essential to avoid errors in reading the image.

Related articles: Chest X-ray for assessing lung health and Pneumonia symptoms, X- ray and diagnosis.

Which type of lung pathologies can be seen in a chest x-ray?

When there are symptoms related to lung disease such as cough (dry or wet), difficulty breathing and chest pain, certain features will be visible for assessment and diagnosis:

• excessive fluid accumulation (pulmonary edema)

• fluid surrounding the lung (pleural effusion)
• lung infections (pneumonia, bronchitis)
• asthma
• cysts
• nodule or tumor 

Chest x-ray images are generally black and white with shades of grey that are related to the density of the structures seen on the image.

• Black or dark: Air
• Dark grey: Fat
• Bright grey: Water (blood, soft tissue)
• Off white: Bone
• Bright white: Metal

A systematic approach to reading x-ray images is recommended before final interpretation of the image for following reasons:

• Detailed reporting of the x-ray findings in the report 
• Rule out co-existing pathologies/abnormalities that might get missed during quick review done at the first instance 
• To identify subtle but likely more sever pathologies if any

What does the systematic approach entail?

The systematic reading, review and assessment of x-ray image involves,

• Close review all the different parts of the image, one by one, to check every other organ and structure that can be seen on the image. 
• Mandatory analysis of all the elements of the image thoroughly instead of quickly winding up the review process when the pathology is spotted. 
• Strictly not reaching the final conclusions about the diagnosis, until each structure, organ and region is systematically and thoroughly inspected.

How to assess if lung x-ray is normal?

To identify the abnormal features of the lungs, familiarity with the normal view of the organs and structures seen on the chest x-ray image, as well as some of the common abnormalities, is required. A systematic approach following the ABCDEFFL mnemonic can be used.

A= Airway – is midline – Check trachea and main-stem bronchi – any deviation, obstruction. Deviated trachea may suggest, tension pneumothorax, lobar collapse, or other mass effect

B= Bones – without fractures or lytic regions

C= Cardiac silhouette (outline of the heart) – spread across less than half of the transverse diameter of the thoracic cavity. The size and shape can help in identifying the disease. It is crisp and has intact border, without pleural fluid or parenchymal opacities. The width of mediastinal is under 8 cm, aortic knob is clearly visible without any disruption to its hump-shaped contour. The aorta is normal.

D= Diaphragm – hemidiaphragms are visible as smooth curves bilaterally and not obscured. There is no air (it appears as bow shaped with relatively low density) under them, the upper portion is not covered by pleural effusion or infiltrates. There is no blunting of the costophrenic angles by pleural effusions. The right hemidiaphragm lies somewhat at higher level than the left.

E= Everything else – Check other structures that surround the lung field, for example subcutaneous soft tissues and pleural boundaries.

F= Field of lungs – should be clear, no opacity related to pleural effusion, parenchymal disease (infectious infiltrate, or mass lesion). Lung vascular margins, specifically in the bottom area, are clearly visible with no indication of pneumothorax. The minor fissure is not prominent and there are no signs of thickening due to fluid accumulation.

Inspect the lung area on the image – any signs of pneumonia, pulmonary edema, pleural effusion or pneumothorax

• Check lung markings stretching to the periphery, 
• visibility of pleural line
• visibility of subcutaneous air
• Density difference of the two hemi thoraces
• Visibility of meniscus
• Visibility of parenchymal opacity
• Presence of air bronchograms – to confirm airspace consolidation
• Presence of cephalization indicating pulmonary edema
• Presence of cavitary lesions indicating abscess or tuberculosis

F= Foreign objects and devices

• Check for foreign bodies – if present, two orthogonal views may be needed to confirm the exact location (whether inside the body or external)
• Check for medical devices – if any, confirm correct positioning
• Endotracheal tube – should be between the carina and suprasternal notch (leaving 1 cm space on both sides)
• Central nervous catheters – should be as per target vein 
• Thoracostomy/chest tubes – all holes on the chest tube are within pleural space
• Nasogastric and orogastric tubes – should be visible vertically in the midline or next to it.
• Pacemaker and automatic implantable cardioverter–defibrillator wires – should not be dislodged or show twists

L= lateral view

Check lateral view image as well when available.

Limitations 

Like any other medical tests, chest x-ray has certain limitations. Normal chest x-ray reading cannot rule out diseases associated with the lung and heart, especially when symptoms related to these organs are present. Further tests are required. Chest x-ray completements clinical and physical findings and should be interpreted in conjunction with these. 

Conclusions

Chest x-ray is widely used in medical practice due to its affordability and speed. Nonetheless, we need to aware of its limitations and to follow a systematic approach to reading images to minimize errors.