11/13/24, 7\:32 PM Guide | CXR interpretation

CXR interpretation

Table of contents
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Introduction

This guide provides a structured approach to chest X-ray interpretation and includes examples of relevant pathology.

Con

Begin chest X-ray interpretation by checking the following details\:
Patient details\: name, date of birth and unique identi
Date and time the
Previous imaging\: useful for comparison.

Assess image quality

Next, you should assess the quality of the image\: a mnemonic you may
.

Rotation

The medial aspect of each clavicle should be equidistant from the spinous processes.
The spinous processes should also be vertically aligned.

Inspiration

The 5-6 anterior ribs, lung apices, both costophrenic angles and the lateral rib edges should be visible.
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Projection

PA).
Note if the

Exposure

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

CXR interpretation (ABCDE)

The ABCDE approach can be used to carry out a structured interpretation of a chest X-ray\:
Airway\: trachea, carina, bronchi and hilar structures.
Breathing\: lungs and pleura.
Cardiac\: heart size and borders.
Diaphragm\: including assessment of costophrenic angles.
Everything else\: mediastinal contours, bones, soft tissues, tubes, valves, pacemakers and review areas.

Airway

Trachea

Inspect the trachea for evidence of deviation\:
The trachea is normally located centrally or deviating very slightly to the right.
If the trachea appears signi
inspect for any paratracheal masses and/or lymphadenopathy.
Causes of true and apparent tracheal deviation
True tracheal deviation\:
Pushing of the trachea\: large pleural e
Pulling of the trachea\: consolidation with associated lobar collapse.
Apparent tracheal deviation\:
Rotation of the patient can give the appearance of apparent tracheal deviation, so as mentioned above, inspect the
clavicles to rule out the presence of rotation.
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Pleural e

Carina and bronchi

The carina is cartilage situated at the point at which the trachea divides into the left and right main bronchus.
On appropriately exposed chest X-ray, this division should be clearly visible. The carina is an important landmark when
assessing nasogastric (NG) tube placement, as the NG tube should bisect the carina if it is correctly placed in the
gastrointestinal tract.
The right main bronchus is generally wider, shorter and more vertical than the left main bronchus. As a result of this
di
bronchus.
Depending on the quality of the chest X-ray you may be able to see the main bronchi branching into further subdivisions of
bronchi.
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Carina & bronchi (normal CXR)

Hilar structures

The hilar consist of the main pulmonary vasculature and the major bronchi.
Each hilar also has a collection of lymph nodes which aren't usually visible in healthy individuals.
The left hilum is often positioned slightly higher than the right, but there is a wide degree of variability between individuals.
The hilar are usually the same size, so asymmetry should raise suspicion of pathology.
The hilar point is also a very important landmark; anatomically it is where the descending pulmonary artery intersects the
superior pulmonary vein. When this is lost, consider the possibility of a lesion here (e.g. lung tumour or enlarged lymph nodes).
Causes of hilar enlargement or abnormal position
Hilar enlargement can be caused by a number of di
Bilateral symmetrical enlargement is typically associated with sarcoidosis.
Unilateral/asymmetrical enlargement may be due to underlying malignancy.
Abnormal hilar position can also be due to a range of di
being pushed (e.g. by an enlarging soft tissue mass) or pulled (e.g. lobar collapse).

Breathing

Lungs

Inspect the lungs for abnormalities\:
When interpreting a chest X-ray you should divide each of the lungs into three zones, each occupying one-third of the
height of the lung.
These zones do not equate to lung lobes (e.g. the left lung has three zones but only two lobes).
Inspect the lung zones ensuring that lung markings are present throughout.
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Compare each zone between lungs, noting any asymmetry (some asymmetry is normal and caused by the presence of
various anatomical structures e.g. the heart).
Some lung pathology causes symmetrical changes in the lung
important to keep this in mind (e.g. pulmonary oedema).
Increased airspace shadowing in a given area of a lung
The complete absence of lung markings should raise suspicion of a pneumothorax.
Right-sided pneumonia [1]

Pleura

Inspect the pleura for abnormalities\:
The pleura are not usually visible in healthy individuals. If the pleura are visible it indicates the presence of pleural thickening
which is typically associated with mesothelioma.
Inspect the borders of each lung to ensure lung markings extend all the way to the edges of the lung
lung markings is suggestive of pneumothorax).
Fluid (hydrothorax) or blood (haemothorax) can accumulate in the pleural space, resulting in an area of increased opacity on
a chest X-ray. In some cases, a combination of air and
resulting in a mixed pattern of both increased and decreased opacity within the pleural cavity.
Tension pneumothorax
A tension pneumothorax is a life-threatening condition which involves an increasing amount of air being trapped within
the pleural cavity displacing (pushing away) mediastinal structures (e.g. the trachea) and impairing cardiac function.
If a tension pneumothorax is suspected clinically (shortness of breath and tracheal deviation) then immediate intervention
should be performed without waiting for imaging as this condition will result in death if left untreated.
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Right-sided pneumothorax [2]

Cardiac

Assess heart size

0.5).
In a healthy individual, the heart should occupy no more than 50% of the thoracic width (e.g. a cardiothoracic ratio of less than
This rule only applies to PA chest X-rays (as AP
heart size from an AP
Cardiomegaly is said to be present if the heart occupies more than 50% of the thoracic width on a PA chest X-ray.
Cardiomegaly can develop for a wide variety of reasons including valvular heart disease, cardiomyopathy, pulmonary
hypertension and pericardial e

Assess the heart's borders

Inspect the borders of the heart which should be well de
The right atrium makes up most of the right heart border.
The left ventricle makes up most of the left heart border.
The heart borders may become di
opacity of overlying lung tissue\:
Reduced de
Reduced de
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Cardiomegaly [2]

Diaphragm

The right hemidiaphragm is, in most cases, higher than the left in healthy individuals (due to the presence of the liver). The
stomach underlies the left hemidiaphragm and is best identi
The diaphragm should be indistinguishable from the underlying liver in healthy individuals on an erect chest X-ray, however,
if free gas is present (often as a result of bowel perforation), air accumulates under the diaphragm causing it to lift and
become visibly separate from the liver. If you see free gas under the diaphragm you should seek urgent senior review, as
further imaging (e.g. CT abdomen) will likely be required to identify the source of free gas.
There are some conditions which can result in the false impression of free gas under the diaphragm, known as pseudo-
pneumoperitoneum, including Chilaiditi syndrome. Chilaiditi syndrome involves the abnormal position of the colon between
the liver and the diaphragm resulting in the appearance of free gas under the diaphragm (because the bowel wall and
diaphragm become indistinguishable due to their proximity). As a junior doctor, you should always discuss a scan that appears
to show free gas with a senior colleague immediately.
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Pneumoperitoneum [3]

Costophrenic angles

The costophrenic angles are formed from the dome of each hemidiaphragm and the lateral chest wall.
In a healthy individual, the costophrenic angles should be clearly visible on a normal chest X-ray as a well de
angle.
Loss of this acute angle, sometimes referred to as costophrenic blunting, can indicate the presence of
in the area. Costophrenic blunting can also develop secondary to lung hyperin
and subsequent loss of the acute angle (e.g. chronic obstructive pulmonary disease).
Left-basal pneumonia [2]
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Everything else

Mediastinal contours

The mediastinum contains the heart, great vessels, lymphoid tissue and a number of potential spaces where pathology can
develop. The exact boundaries of the mediastinum aren't particularly visible on a chest X-ray, however, there are some
important structures that you should assess.
Aortic knuckle
The aortic knuckle is located at the left lateral edge of the aorta as it arches back over the left main bronchus. Reduced
de
Aortopulmonary window
The aortopulmonary window is a space located between the arch of the aorta and the pulmonary arteries. This space can
be lost as a result of mediastinal lymphadenopathy (e.g. malignancy).
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