Chest X-ray Interpretation Flashcards
How do you assess the image quality of a CXR?
RIPE
Rotation: medial aspect of clavicle should be equidistant from spinous processes which should also be vertically oriented against vertebral bodies
Inspiration: 5-6 anterior ribs (i.e. the ones curving around the sides); c. posterior ribs; lung apices, both costophrenic angles and lateral rib edges should be visible
Projection: AP vs PA vs lateral
- If no label or if scapulae not projected within chest = PA = standard
- Lateral = labelled with the side closest to the cassette e.g. Left lateral
- AP - often bedside projections; beam diverges meaning the magnification of structures i.e. cant accurately tell heart size
Exposure: left hemidiaphragm should be visible as should vertebrae behind the heart; should be good contrast between lung/background and rib
What is the ABCDE approach to CXR interpretation?
May also want to check your commonly missed areas first i.e. lines
Airway:
- Trachea
- Carina
- Bronchi
- Hilar structures
Breathing = lungs, pleura
Cardiac:
- Heart size
- Borders
Diaphragm + costophrenic angles
Everything else: https://radiopaedia.org/articles/chest-radiograph-assessment-using-abcdefghi?lang=gb (ABCDEFGHI) - Airway - Bones - Cardiac
- Mediastinal contours
- Bones
- Soft tissue
- Tubes
- Valves
- Pacemakers
What signs are you looking for when assessing airway?
Trachea:
- Normally central
- Deviates towards pathology in lung collapse (atelectasis), pleural fibrosis
- Deviates away from pathology in tension pneumothorax, pleural effusion, large mass
- Any paratracheal mass or lymphadenopathy
Carnia + bronchi:
- Bifurcation of trachea - at the level of T4/5; should be bisected by correctly placed NG tube (e.g. because it is not in the trachea)
- R main bronchus - largest + highest so most likely place for inhaled foreign body (or misplaced ET tube - should be higher in the trachea above the carnia)
Hilar structures:
- Pulmonary vasculature and major bronchi + lymph nodes (not visible in healthy), usually symmetrical so asymmetry = ?pathology e.g. malignancy; bilateral enlargement associated with sarcoidosis
- Hilar points = > / < shapes on the R and L respectively; R should be lower than the L due to passage of pulmonary arteries
What signs are you looking for when assessing breathing?
Describe according to upper, middle and lower zones
Lungs:
- Lung markings throughout all parts? Even on both sides?
- Focal shadowing may indicate consolidation (from infection; contusion-usually next to injured bones) or malignancies
- Complete absence of markings may indicate pneumothorax
- Costophrenic angles - nice and sharp; diffuse, homogenous shadowing/bluntening of angles +/- meniscus (fluid level reaching up the ribs) in pulmonary effusion
Pleura:
- Not normally visible in healthy individuals unless abnormality e.g. pleural thickening in mesothelioma
- Inspect lung borders - markings should extend all the way to edge of lung fields, if absence in area with appearing decreased density then consider pneumothorax
What do you look for when assessing cardiac features?
Heart size:
- Healthy - should be no more than 50% thoracic width/cardiothoracic ratio of <0.5 on PA XR (AP will exaggerate the size)
- If larger - cardiomegaly e.g. valvular disease, cardiomyopathy, pulmonary HTN, pericardial effusion, aortic dissection etc etc.
Heart borders:
- R atrium is most of the R border - loss of definition associated with R middle lobe consolidation
- L ventricle is most of the L border - loss of definition associated with L upper lobe consolidation
What do you look for when assessing the diaphragm?
Right hemi-diaphragm:
- Higher in most cases, due to liver - should be indistinguishable from the liver in an erect XR; if gas separates diaphragm/liver from underneath then think bowel perforation - CT and senior review
Left hemi-diaphragm:
- Stomach sits below, identifiable by gastric bubble
Costophrenic angles:
- Should be clearly visible at an acute angle in the healthy
Loss/blunting of angles = fluid (e.g. heart failure), consolidation (e.g. pneumonia), or hyperinflation e.g. COPD (but this will be associated with a flat hemidiaphragm)
Cardiophrenic angles - should also be nice a crisp
How do you assess ‘everything else’?
Mediastinal contours:
- Contains heart, great vessels, lymphoid tissue
- Borders aren’t particularly visible on CXR but can visualise:
- Aortic knuckle = left lateral edge of aorta as it arches over L main bronchus; loss of definition could be an aneurysm
- Aorto-pulmonary window = space between aortic knuckle and pulmonary arteries - space may be lost due to mediastinal lymphadenopathy (?malignancy, TB)
Bones:
-Any fractures? Calluses? Sclerotic sites?
Soft tissues:
- Large haematomas? Swelling?
Tubes/valves/pacemakers:
- NG tube safely placed? (E.g. not going to aspirate)
- Central line, ECG cables, artificial valves, pacemaker (often below left clav)
Review areas: (commonly missed serious pathology)
- Apices
- Hilar
- Behind the heart
What is surgical emphysema? What causes it and how does it present on CXR?
Aka subcutaenous emphysema
Air/gas is located in the subcutaneous tissues/under the skin
Caused by:
- Pneumothorax, pnemomediastinum, perforated hollow viscus in the neck e.g. oesophagus
- Penetrating trauma* including surgery
Clinically felt as crepitus, soft tissue swelling and discomfort
CXR:
- Striated lucencies in the soft tissues that may outline muscle fibres
What is an air bronchogram? What are possible causes?
Air-filled bronchi (dark) being made visible by the opacification of surrounding alveoli (grey/white)
It is almost always caused by a pathologic airspace/alveolar process, in which something other than air fills the alveoli
- Consolidation
- Oedema
- Haemorrhage or infarct
- Neoplasm
- ILD
Air bronchograms will not be visible if the bronchi themselves are opacified (e.g. by fluid) and thus indicate patent proximal airways
What are the CXR findings in COPD?
Hyperinflation = >7 anterior, >9 posterior ribs seen in the lung fields
Flattening of the hemi-diaphragms
How do you assess bones on CXR?
The clavicle and ribs act as landmarks when assessing the adequacy of inspirationtaken by the patient
(The rib under the clavicle is the 4th)
The anterior end of approximately 5-7 ribs should be visible above the point at which the mid-clavicular line intersects the diaphragm
- Less than 5 ribs indicates incomplete inspiration
- More than 7 ribs suggests lung hyper-expansion
The subcostal grooves run along the underside of the ribs and contain vessels and subcostal nerves
- To avoid damaging the subcostal nerves or vessels the superior edge of a rib is used as the landmark during procedures such as chest drain insertion
Healed fractures- areas of sclerosis, possible incomplete union
Metastases - darker or lighter areas of bone (?)
How many lung fissures can be seen on aCXR?
On a frontal view, often just the horizontal fissure in the R lung
On the lateral views you can often see overlapping oblique fissures (though patient rotation will alter)
Alveolar vs interstitial disease features
Alveolar: Shadowing = - Fluffy/blobby - Ill defined margins - Coalescing, merging - Segmental, lobar Additional features = - Air bronchograms DDx = Pulmonary oedema, lobar pneumonia, haemorrhage, lymphoma, bronchial carcinoma, ARDS
Interstitial: Shadowing = - Small nodules - Linear/reticular +/- septal lines - Reticulo-nodular Additional features = - Reduced lung volume DDX = - Pulmonary oedema, viral/PCP pneumonia, TB, sarcoidosis, RA, scleroderma, pulmonary fibrosis
When should you repeat CXRs in pneumonia?
Throughout hospital stay to check for resolution, and certainly before discharge
Also, weeks-months after discharge to check there is not an underlying cancer or other pathology that was masked during the in patient stay
What are the fearures of pulmonary oedema?
MORE
Wider, upward pointing vessels in the upper zones near the hilum = upper lobe venous dilatation from venous congestion
Air bronchograms
‘Batwinging’ - perihilar opacity
Kerley B lines = horizonal lines meeting the rib margins;
Alveolar opacities
Costophrenic angle blunting
Also cardiomegaly
