How Do I Make Sense of Chest X-Rays? Flashcards
What is the ideal complete chest x-ray?
Erect
Posteroanterior (PA) and lateral
Why is PA preferred to anteroposterior (AP)?
AP magnifies heart
In PA see more of lung fields
What is a projection in x-rays?
Way an x-ray is taken; eg:
- PA
- Lateral
Why is the lateral projection usually left lateral?
Places heart closer to film
What does a left lateral projection mean?
Left side of patient closest to x-ray film
If a patient is sitting upright, is the x-ray considered erect?
Yes
Why are AP chest films usually done?
Patient very unwell/unable to stand
What does a frontal projection describe?
AP
PA
What is a mobile x-ray?
X-ray taken with mobile x-ray machine
Why might a chest x-ray be performed supine?
If patient is very unwell
Not possible/unsafe to sit patient upright
What should you check first in a chest x-ray?
Name Date Other labels - Mobile - AP - Supine - Side marker = L/R
What do you normally see in lung fields as opaque structures?
Pulmonary arteries
Pulmonary veins
Don’t normally see airways
Where are pulmonary vessels larger when seen on an erect chest x-ray?
Towards lung bases due to hydrostatic effect
How do you measure heart size?
Cardiothoracic ratio <50% on PA film with good inspiration
What is the cardiothoracic ratio?
Max cardiac transverse dimension/max transverse lung dimension
When can a normal heart size appear larger on a chest x-ray?
AP - 10% larger
Supine - at least 20% larger
Poor inspiration
Why is a chest x-ray taken on inspiration?
Doesn’t magnify heart size
Allows clearer view of lung fields
What is the effect of a supine film?
Heart looks bigger
Lungs look smaller and congested
How do you gauge lung volume on a chest x-ray?
Count number of anterior ribs visible
Normal = 5-6.5 anterior ribs
How does lung volume change on a chest x-ray in COPD?
Lung volumes expand in sagittal dimension, and top and bottom
What does increased retrosternal lucency mean?
Increased area behind sternum
What does the diaphragm look like in a chest x-ray with hyperinflated lungs?
Flattened
What creates increased opacity in lung fields?
Pleural fluid Collapse of part/all of lung Fluid/cells in airspaces - Oedema - Infective consolidation Fluid/cells in lung interstitium - Oedema - Inflammatory change Tumours/other masses in lung
What does a pleural effusion typically look like?
At base
Meniscus curves up chest wall
Becomes less opaque more superiorly
What are some causes of pleural effusion?
Infection
Cardiac failure
Blood > haemothorax
Pus > empyema
Are pleural effusions unilateral or bilateral?
Depends on cause
What does atelectasis typically look like?
Collapse > loss of volume > increased opacity of affected zone
Possible silhouette sign?
What is the silhouette sign?
Loss of silhouette that normally occurs when air lies adjacent to soft tissue structure and creates silhouette outline
What does fluid or cells in the alveoli typically look like?
Called airspace/alveolar opacity
Fluffy
+/- bronchograms
Often bounded by fissures
What are air bronchograms?
Airways appear less opaque because still contain air
What does interstitial lung field opacity typically look like?
Lines +/- dots
What are the common causes of interstitial lung field opacity?
Pulmonary oedema
Atypical infection
Pulmonary fibrosis
Malignant infiltrate
What are Kerley B lines?
Horizontal lines
Less than 2 cm long
Commonly found in lower zone periphery
Thickened oedematous interlobular septa
How do you confirm the position of a pathology on a chest x-ray?
Confirm using both frontal and lateral films
What do masses typically look like on a chest x-ray?
Usually rounded
May contain gas because of cavitation
What are the commonest causes of masses in a chest x-ray?
Cancer
Abscess
What are the common causes of lung opacity due to multiple nodules?
Most often due to pulmonary metastases from distant tumour
Occasionally infective causes
What are the commonest causes of increased lucency in a lung field?
Pneumothorax Bullous emphysema, especially if asymmetrical Others - Lobar collapse - Pulmonary embolism
When you suspect a pneumothorax, why should you take both an inspiratory and expiratory image?
Expiratory film makes pneumothorax more obvious
- Helpful for detecting small pneumothoraces
What does a pneumothorax typically look like on a chest x-ray?
Usually see lung edge
Increased lucency
Hemidiaphragm depressed on expiratory film
Where is bullous emphysema more commonly seen?
Upper zones of lung fields
