Interpreting Chest Radiographs Flashcards
1
Q
When should a CXR be requested?
A
- SOB
- Acute chest pain
- Investigation for malignancy
- Following severe trauma
- Pneumonia
- Chronic lung diseases
- Pleural diseases
- Peritonitis
2
Q
What densities can be seen on CXR?
A
- Air
- Fat
- Fluid / soft tissue
- Bone
- Metal
3
Q
What is always the first step when looking at a CXR?
A
-
Confirm patient details
- Name / DOB
- Date the film was taken
- Check if there is any previous imaging (can be useful for comparison).
4
Q
Describe the assessment of image quality of a CXR.
A
-
Rotation
- The medial aspect of each clavicle must be equidistant from the spinous processes.
- The spinous processes should be vertically orientated against the vertebral bodies.
-
Inspiration
- 5-6 anterior ribs, the lung apices, both costophrenic angles and lateral rib edges should be visible.
-
Projection
- AP vs PA film
- Tip - if there is no label, assume it is PA. Also, if the scapulae are not projected within the chest, it is PA.
-
Exposure
- Left hemidiaphragm visible to the spine and vertebrae visible behind the heart.
5
Q
Describe CXR interpretation.
A
- ABCDE
-
Airway
- Trachea
- Carina and bronchi
- Hilar structures
-
Breathing
- Lungs
- Pleura
-
Cardiac
- Assess heart size
- Assess heart borders
-
Diaphragm
- Costophrenic angles
-
Everything else
-
Mediastinal contours
- Aortic knuckle
- Aortic-pulmonary window
- Bones
- Soft tissue
- Tubes / valves / pacemakers
- Review areas
-
Mediastinal contours
6
Q
Describe the A in CXR interpretation.
A
Look at the airways.
- Trachea
- Carina and bronchi
- Hilar structures
7
Q
What things are you looking for in the trachea on a CXR?
A
- The trachea is normally located centrally or just slightly off to the right.
- If the trachea is deviated, look for anything that could be pushing or pulling the trachea.
- Also inspect for any paratracheal masses / lymphadenopathy.
- Pushing of trachea - e.g. large pleural effusion / tension penumothorax.
- Pulling of trachea - e.g. consolidation with lobar collapse.
- Note - rotation of the patient can give the appearance of a deviated trachea, so as mentioned above, check the clavicles to rule out rotation as the cause.
8
Q
What things are you looking for in the carina and bronchi on a CXR?
A
- Carina should be visible on CXR - it is important landmark when assessing nasogastric tube placement, as the NG tube should bisect the carina if it is correctly placed (i.e. not in the airway).
- The right main bronchus is generally wider, shorter and ore vertical than the left main bronchus.
- As a result, it is more common for inhaled foreign objects to become lodged here.
- Depending on CXR quality, you may be able to see the main bronchi branching into further subdivisions of bronchi which supply each lobe.
9
Q
What things are you looking for in the hilar structures on a CXR?
A
- The hila consist of the main pulmonary vasculature and the major bronchi.
- Each hilum also has a collection of lymph nodes which aren’t usually visible in healthy individuals.
- The left hilum if often positioned slightly higher than the right, but there is a wide degree of variability between individuals.
- The hila 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, think of a lesion here (e.g. lung tumour or enlarged lymph nodes).
- You should look for any evidence of the hilum being pushed (e.g. by an enlarging soft tissue mass) or pulled (eg. lobar collapse).
10
Q
Which pathologies can cause hilar enlargement?
A
- Bilateral symmetrical enlargement is typically associated with sarcoidosis.
- Unilateral / asymmetrical enlargement may be due to underlying malignancy.
11
Q
Describe the B in CXR interpretation.
A
Breathing
- Inspect the lungs
- Inspect the pleura
12
Q
What things are you looking for in the lungs on CXR?
A
- When looking at a CXR, divide each of the lungs into 3 zones, each occupying 1/3 of the height of the lung (≠ lobes).
- Inspect each of the zones of the lung, first ensuring that lung markings ocupy the entire zone.
- Compare each zone between lungs, paying close attention for 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 fields, which can make it more difficult to recognise, so it’s important to keep this in mind (e.g. pulmonary oedema).
- Increased airspace shadowing in a given area of the lung field may suggest pathology (e.g. consolidation / malignant lesion).
- The complete absence of lung markings within a segment of the lung field should raise suspicion of pneumothorax.
13
Q
What things are you looking for in the pleura on a CXR?
A
- The pleura are not normally visible in healthy individuals, unless there is an abnormality such a pleural thickening.
- Inspect te borders of each of the lungs to ensure lung markings extend all the way to the edges of the lung fields (if there appears to be an area lacking lung markings with decreased density this may suggest the presence of a pneumothorax).
- Fluid (hydrothorax) or blood (haemothorax) can also accumulate in the pleural space, causing an area of increased opacity or a combination of both a pneumothorax and fluid (hydropneumothorax).
- Pleural thickening can be caused by mesothelioma.
14
Q
What should be reassessed on a CXR if you suspect pneumothorax?
A
- If pneumothorax suspected, you should reassess the trachea for evidence of deviation away from the pneumothorax which would be in keeping with a tension pneumothorax.
- This is a medical emergency requiring immediate intervention.
- If a tension pneumothorax is suspected clinically (SOB and tracheal deviation) then immediate intervention should be performed without waiting for imaging as this condition will result in death if left untreated.
15
Q
Describe the C in CXR interpretation.
A
Cardiac
- Assess heart size
- Assess heart borders
17
Q
Describe how to assess heart borders on a CXR.
A
- Inspect the borders of the heart which should be well defined in healthy individuals:
- The right atrium makes up most of the right heart border.
- The left ventricle makes up most of teh left heart border.
- The heart borders may become difficult to distinguish from the lung fields as a result of various pathological processes (e.g. consolidation) which cause increased opacity of the lung tissue.
- Loss of definition of the right heart border is associated with right middle lobe consolidation.
- Loss of definition of the left heart border is associated with lingular consolidation.
18
Q
Describe the D in CXR interpretation.
A
Diaphragm.
- The right hemi-diaphragm is, in most cases higher than the left in healthy individuals (underlying liver).
- The stomach underlies the left hemi-diaphragm and is best identified by the gastric bubble located within it.
- The diaphragm should be indistinguishable from the underlying liver in healthy individuals on an erect CXR, however if free gas is present (often as a result of bowel perforation), air accumulates under the diaphragm causing it to lift and become bisibly 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.
19
Q
What are the possible causes of a CXR looking like there is air under the diaphragm?
A
- There are some conditions which give the appearance of free gas under the diaphragm (pseudo-pneumoperitoneum), such as Chilaiditi syndrome which involves the colon becoming positioned between the liver and diaphragm (because the bowel wall and diaphragm become indistinguishable due to their proximity).
- As a result the imaging needs to be considered in the context of the patient’s history and your findings on clinical examination.
20
Q
What are the things you are looking for in the costophrenic angles on a CXR?
A
- The costophrenic angles are formed from the dome of each hemi-diaphragm and the lateral chest wall.
- In a healthy individual the costo-phrenic angles should be clearly visible on a normal CXR as a well-defined acute angle.
- Loss of this acute angle (referred to as costophrenic blunting) can suggest the presence of fluid or consilidation in the area.
- Costophrenic blunting can also occur secondary to lung hyperinflation (seen in diseases such as COPD) as a result of diaphragmatic flattening and subsequent loss of the acute angle.
22
Q
Describe what you are looking for when inspecting mediastinal contours on a CXR.
A
- Aortic knuckle:
- Left lateral edge of the aorta as it arches back over the left main bronchus.
- Loss of definition of the aortic knuckles contours can be caused by an aneurysm.
- Aorto-pulmonary window:
- The aorto-pulmonary 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).
