How Do I Make Sense of Chest X-Rays?

Question 1

What is the ideal complete chest x-ray?

Answer 1

Erect

Posteroanterior (PA) and lateral

Question 2

Why is PA preferred to anteroposterior (AP)?

Answer 2

AP magnifies heart

In PA see more of lung fields

Question 3

What is a projection in x-rays?

Answer 3

Way an x-ray is taken; eg:

• PA
• Lateral

Question 4

Why is the lateral projection usually left lateral?

Answer 4

Places heart closer to film

Question 5

What does a left lateral projection mean?

Answer 5

Left side of patient closest to x-ray film

Question 6

If a patient is sitting upright, is the x-ray considered erect?

Answer 6

Yes

Question 7

Why are AP chest films usually done?

Answer 7

Patient very unwell/unable to stand

Question 8

What does a frontal projection describe?

Answer 8

AP

PA

Question 9

What is a mobile x-ray?

Answer 9

X-ray taken with mobile x-ray machine

Question 10

Why might a chest x-ray be performed supine?

Answer 10

If patient is very unwell

Not possible/unsafe to sit patient upright

Question 11

What should you check first in a chest x-ray?

Answer 11

Name
Date
Other labels
- Mobile
- AP
- Supine
- Side marker = L/R

Question 12

What do you normally see in lung fields as opaque structures?

Answer 12

Pulmonary arteries
Pulmonary veins
Don’t normally see airways

Question 13

Where are pulmonary vessels larger when seen on an erect chest x-ray?

Answer 13

Towards lung bases due to hydrostatic effect

Question 14

How do you measure heart size?

Answer 14

Cardiothoracic ratio <50% on PA film with good inspiration

Question 15

What is the cardiothoracic ratio?

Answer 15

Max cardiac transverse dimension/max transverse lung dimension

Question 16

When can a normal heart size appear larger on a chest x-ray?

Answer 16

AP - 10% larger
Supine - at least 20% larger
Poor inspiration

Question 17

Why is a chest x-ray taken on inspiration?

Answer 17

Doesn’t magnify heart size

Allows clearer view of lung fields

Question 18

What is the effect of a supine film?

Answer 18

Heart looks bigger

Lungs look smaller and congested

Question 19

How do you gauge lung volume on a chest x-ray?

Answer 19

Count number of anterior ribs visible

Normal = 5-6.5 anterior ribs

Question 20

How does lung volume change on a chest x-ray in COPD?

Answer 20

Lung volumes expand in sagittal dimension, and top and bottom

Question 21

What does increased retrosternal lucency mean?

Answer 21

Increased area behind sternum

Question 22

What does the diaphragm look like in a chest x-ray with hyperinflated lungs?

Answer 22

Flattened

Question 23

What creates increased opacity in lung fields?

Answer 23

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

Question 24

What does a pleural effusion typically look like?

Answer 24

At base
Meniscus curves up chest wall
Becomes less opaque more superiorly

Question 25

What are some causes of pleural effusion?

Answer 25

Infection
Cardiac failure
Blood > haemothorax
Pus > empyema

Question 26

Are pleural effusions unilateral or bilateral?

Answer 26

Depends on cause

Question 27

What does atelectasis typically look like?

Answer 27

Collapse > loss of volume > increased opacity of affected zone
Possible silhouette sign?

Question 28

What is the silhouette sign?

Answer 28

Loss of silhouette that normally occurs when air lies adjacent to soft tissue structure and creates silhouette outline

Question 29

What does fluid or cells in the alveoli typically look like?

Answer 29

Called airspace/alveolar opacity
Fluffy
+/- bronchograms
Often bounded by fissures

Question 30

What are air bronchograms?

Answer 30

Airways appear less opaque because still contain air

Question 31

What does interstitial lung field opacity typically look like?

Answer 31

Lines +/- dots

Question 32

What are the common causes of interstitial lung field opacity?

Answer 32

Pulmonary oedema
Atypical infection
Pulmonary fibrosis
Malignant infiltrate

Question 33

What are Kerley B lines?

Answer 33

Horizontal lines
Less than 2 cm long
Commonly found in lower zone periphery
Thickened oedematous interlobular septa

Question 34

How do you confirm the position of a pathology on a chest x-ray?

Answer 34

Confirm using both frontal and lateral films

Question 35

What do masses typically look like on a chest x-ray?

Answer 35

Usually rounded

May contain gas because of cavitation

Question 36

What are the commonest causes of masses in a chest x-ray?

Answer 36

Cancer

Abscess

Question 37

What are the common causes of lung opacity due to multiple nodules?

Answer 37

Most often due to pulmonary metastases from distant tumour

Occasionally infective causes

Question 38

What are the commonest causes of increased lucency in a lung field?

Answer 38

Pneumothorax
Bullous emphysema, especially if asymmetrical
Others
- Lobar collapse
- Pulmonary embolism

Question 39

When you suspect a pneumothorax, why should you take both an inspiratory and expiratory image?

Answer 39

Expiratory film makes pneumothorax more obvious

- Helpful for detecting small pneumothoraces

Question 40

What does a pneumothorax typically look like on a chest x-ray?

Answer 40

Usually see lung edge
Increased lucency
Hemidiaphragm depressed on expiratory film

Question 41

Where is bullous emphysema more commonly seen?

Answer 41

Upper zones of lung fields