Lecture 11- Chest X-ray part 1 Flashcards
begin chest x-ray interpretation by checking the following details
Patient details: name, date of birth and unique identification number.
Date and time the film was taken
Previous imaging: useful for comparison.
assess image quality by using
RIPE
R for rotation
rotation requirments
- The medial aspect of each clavicle should be equidistant from the spinous processes.
- The spinous processes should also be in vertically orientated against the vertebral bodies.
I
inspiration
Inspiration requirements
The 5-6 anterior ribs, lung apices, both costophrenic angles and the lateral rib edges should be visible.
P for
projection
projection requirement
Note if the film is AP or PA: if there is no label, then assume it’s a PA film (if the scapulae are not projected within the chest, it’s PA).
E for
exposure
exposure requirements
The left hemidiaphragm should be visible to the spine and the vertebrae should be visible behind the heart.
ABCDE approach can be used to carry out a
structured interpretation of a chest X-ray
ABCDE approach
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 significantly deviated, inspect for anything that could be pushing or pulling the trachea. Make sure to inspect for any paratracheal masses and/or lymphadenopathy.
Causes of true tracheal deviation
- Pushing of the trachea: large pleural effusion or tension pneumothorax.
- Pulling of the trachea: consolidation with associated lobar collapse.
causes of 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.
Pleural effusion with tracheal deviation
airways: 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.
features of the right main bronchus
The right main bronchus is generally wider, shorter and more vertical than the left main bronchus.
As a result of this difference in size and orientation, it is more common for inhaled foreign objects to become lodged in
the right main bronchus.
airway : 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 ……….. than the right, but there is a wide degree of variability between individuals.
higher
The hilar are usually the same size, so asymmetry should raise suspicion of pathology.
why is the hilar point and important landmark
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).
Hilar enlargement can be caused by a number of different pathologies:
- 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 different pathologies. You should inspect for evidence of the hilar being pushed (e.g. by an enlarging soft tissue mass) or pulled (e.g. lobar collapse).
breathing: lungs
inspect the lungs for abnormalities
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.
- 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 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 a lung field may indicate pathology (e.g. consolidation/malignant lesion).
- The complete absence of lung markings should raise suspicion of a pneumothorax.
breathing: inspecting 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 fields
the absence of lung markings is suggestive of
pneumothorax
what can accumulate in the pleural space
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 fluid can accumulate in the pleural space (hydropneumothorax), 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.
Cardiac: heart size in healthy
In a healthy individual, the heart should occupy no more than 50% of the thoracic width (e.g. a cardiothoracic ratio of less than 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 0.5)….
This rule only applies to:
PA chest X-rays (as AP films exaggerate heart size), so you should not draw any conclusions about heart size from an AP film.
……………………… is said to be present if the heart occupies more than 50% of the thoracic width on a PA chest X-ray.
Cardiomegaly
Cardiomegaly can develop for a wide variety of reasons including
valvular heart disease, cardiomyopathy, pulmonary hypertension and pericardial effusion.
cardiac: assessing heart borders
The heart borders may become difficult to distinguish from the lung fields as a result of
pathology which increases the opacity of overlying lung tissue:
Reduced definition of the right heart border is typically associated with
right middle lobe consolidation.
Reduced definition of the left heart border is typically associated with
lingular consolidation.
The left lung, unlike the right does not have a middle lobe. However the term lingula is used to denote a projection of the upper lobe of the left lung that serves as the homologue.
Diaphragm: right hemidiaphragm is , ……. than the left in healthy individuals (due to presence of the liver)
right hemidiaphragm is , higher than the left in healthy individuals (due to presence of the liver)
what underlies the left hemidiaphragm
The stomach underlies the left hemidiaphragm and is best identified by the gastric bubble located within it
The diaphragm should be indistinguishable from the underlying l
iver in healthy individuals on an erect chest X-ray,
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 ……………………….. , including …………………. syndrome.
pseudo-pneumoperitoneum
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.
Diaphragm: costaphrenic angles
costophrenic angles are formed from the dome of each hemidiaphragm and the lateral chest wall.
cardiophrenic angle
In a healthy individual, the costophrenic angles should be
clearly visible on a normal chest X-ray as a well defined acute angle
clearly visible on a normal chest X-ray as a well defined acute angle.
can indicate the presence of fluid or consolidation in the area.
Costophrenic blunting can also develop secondary to
lung hyperinflation as a result of diaphragmatic flattening and subsequent loss of the acute angle (e.g. chronic obstructive pulmonary disease).
everything else: mediastinal contour.
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
- aortopulmonary window
aortic knuckle
is located at the left lateral edge of the aorta as it arches back over the left main bronchus.
Reduced definition of the aortic knuckle contours can occur in the context of an
aneurysm.
aortopulmonary window is a space located between
the arch of the aorta and the pulmonary arteries.
aortopulmonary window space can be lost as a result of
mediastinal lymphadenopathy (e.g. malignancy).
everything else: bones
Inspect the visible skeletal structures looking for abnormalities (e.g. fractures, lytic lesions).
everything else: soft tissue
Inspect the soft tissues for obvious abnormalities (e.g. large haematoma).
everything else: Tubes, valves and pacemakers
Tubes
Nasogastric tube placement is something you’ll often be asked to assess on a chest X-ray to confirm safe placement for feeding. See our NG tube placement guide for more details.
everything else: Tubes, valves and pacemakers
valves
Artificial heart valves
Artificial heart valves typically appear as ring-shaped structures on a chest X-ray within the region of the heart (e.g. aortic valve replacement).
Everything else: Tubes, vakves and pacemakers:
Lines
Lines
Various tubes and cables will be visible as radio-opaque lines on the chest X-ray (e.g. central line, ECG cables).
everything else: Tubes, valves and pacemakers
Pacemaker
Pacemakers typically appear as a radio-opaque disc or oval in the infraclavicular region connected to pacemaker wires which are positioned within the heart.
Finally, before completing your assessment of a chest X-ray, make sure you’ve looked at the ‘…………. …………….’ where pathology is often missed.
review areas
review areas
- the lung apices
- the retrocardiac region
- behind the diaphragm
- the peripheral region of the lungs
- the hilar regions
