The Chest X-ray

system
abnormalities
System
A systematic approach is necessary.
More is missed by not looking than by not knowing.
* Remember: CXR findings often lag behind clinical findings.
Also remember to compare with previous films.
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Basics
Name & date.

L and R markers
Is it really dextrocardia, or have the stickers been put on wrong (note stomach gas vs apex).

Position & Projection
PA erect is ideal
- many portables are done AP, which diverge from heart to film
--> so exaggerate heart size.
Supine films cause distension of all posterior vessels occurs
--> lung fields appear plethoric
--> small effusions may be missed & the heart appears bigger.

Rotation
Note turning and accentuation of hila.
Medial ends of the clavicles should be equidistant from the midline spinous processes.

Penetration
Should just see through mediastinum to vertebral bodies.
Good technique will have scapulae outside lung fields.

Inspiration
Full inspiration - allows no basal crowding of pulmonary vessels, hence accurate assessment of cardiothoracic ratio.
Diaphragm should be at 10th, 11th rib posteriorly, or at 6th costal cartilage anteriorly (5th-7th = ok).
R hemidiaphragm ~2cm higher than L.
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Obvious abnormality
Overall chest shape
Note obvious abnormality first
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Mediastinum
Trachea
?Midline.
Deviates if goitre or mediastinal mass.
Normally deviates a little left as it passes the aortic knuckle.

Mediastinum deviation
(Including trachea).
Eg if large pleural effusion, tension pneumothorax, pulmonary collapse.
NB - rotation of pt can lead to apparent distortion.

Width
?aortic features.
Note that aortic arch becomes wider and unfolded with age anyway because of loss of elasticity.

Tubes and lines
Check positions.
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Hila
Anatomy
Mostly pulmonary arteries, with upper lobe veins superimposed.
L higher than R.
L squarish, R v-shaped.
?Enlargement
Eg Lymphadenopathy, large pulmonary artery.
NB - prominent in rotation.
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Heart
Anatomy
2/3 to left of spine.
R heart border formed by outer border of R atrium
L heart border by L ventricle.
L margin of R ventricle lies about a thumb's breadth in from the left heart border (LAD zone on heart).
?Enlargement
If size >50% transthoracic diameter on PA projection.
Valve calcification - better on lateral view, as can't be seen over spine.
- apparent cardiomegaly seen in: chamber enlargement (athletes), AP projection, high diaphragm, cardiac fat pads, skeletal deformity.
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Diaphragm
Anatomy
Hemidiaphragms on frontal films are top of domes seen tangentially.
Most costophrenic lung tissue is not seen.
Abnormalities
?Hyperinflation, low and flat.
Free air.
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Lungs
Anatomy:
3 lobes on R, 2 on L.
- easier to talk of arbitrary upper / middle / lower zones.
- compare them for densities, distribution of vascular markings.
- upper zones from apices to 2nd costal cartilage.
- mid zones from 2nd-4th CCs.
- lower between 4th-6th CCs.
Radiolucency of lungs is due to air, greyness due to pulmonary vessels.
Upper zones normally less perfusion as smaller vessels.

Congestion
- unwise to make too precise a stab at underlying pathology.
?Upper zone vessel congestion / diversion.
?Opacity, consolidation, patchy shadowing.
- look near and far.

Others
Check lungs go right to side of the ribs.
? Pneumothorax or effusion.
Fissures
- hairline shadows, horizontal fissure at R 4th CC, oblique fissures not seen on frontal view.
Crisp edges at costophrenic angles, diaphragm and heart border.
Parenchymal volume - high in obstruction, low in poor effort, abdo distension etc.
Costophrenic angles for fluid.c
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Bones & Soft Tissues

Shadows
Nipple shadows often over lower zones - don't confuse with a 'coin' lesion.
Breast shadows - note if missing, + ?pulmonary / bony mets, or upper zone post-radiation fibrosis.

Air
Surgical emphysema.

Bones
RCS's: ribs, clavicles, scapulae, sternum.

Others
Foreign bodies
Calcified tuberculous glands in neck, if pt has lung scarring or calcified hilar nodes.
Rib fractures, SOLs.
Rib notching due to increased vessel flow (eg coarctation).
Cervical ribs, thoracic scoliosis.
Joint erosions, arthritis.
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Review
Double check certain parts if it appears unexpectedly normal:
Retrocardiac region for collapsed left lower lobe
- triangular opacity behind heart shadow.
Apices - lesions, especially TB, Pancoast tumours.
Lung field translucency - subtle pneumothorax sign is difference in translucency of the 2 lungs.
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Lateral
Useful mainly for localisation, in 3D of a visible lesion. Examine it just as carefully though, as sometimes a lesion only seen in lateral.
Points to note:
Retrosternal, retrocardiac triangles normally of similar radiodensity.
Thoracic vertebrae become less opaque lower down the spine, unless there is pulmonary / pleural disease.
Posterior costophrenic angle is sharp unless there is fluid or adjacent consolidation.
Hemidiaphragms are well defined unless there is pleural or pulmonary disease.
Oblique fissure placement is '4 to 4'. Ie from ~4cm behind ant costophrenic angle through the hilum to the T4 vertebral body level.
Heart: RV forms anterior heart border in lateral, Left atrium forms upper post border.
Mitral valve calcification seen below an imaginary line drawn from the anterior costophrenic angle to the hilum, aortic valve calcification above this line.
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Checklist
A - Airway (midline, deformities, masses).
B - Bones & soft tissue (fractures, subcutaneous emphysema).
C - Cardiac size, silhouette, retrocardiac density.
D - Diaphragms (R above left, costophrenic angles sharp, sharp contrast adjacent to lungs.
E - Equal volume (count ribs, look for mediastinal shift).
F - Fields (pleura and lung parenchyma).
G - Gastric bubble (no more than 0.5 cm wide opacity above air bubble.)
H - Hilum (L above R, no larger than a thumb. (& Hardware).

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Abnormalities

Air Bronchograms
Bronchus is not normally visible as both sides of it are radio-opaque equally.
- if normal lung loses aeration, the bronchus will be visible.
- suggests: oedema, infection, other infiltrate.

Kerley B lines
Horizontal lins meeting at pleural surface at right angles.
1-2cm long, 1-2mm thick.
- suggests: fluid or tissue in intralobular septa.

COPD
Increased lung lucency, general loss of vascularity
- lung fields are increased in size.

Pleural Effusions
Blunts the costophrenic angle (small)
Compresses the lung, flattens the diaphragm and moves the mediastinum (large).
- sit patient up for 15 minutes and take it erect for better sensitivity

Consolidation
Will not produce mediastinal shift unless collapse is significant

Pericardial Effusion
Enlarged cardiac silhouette is not specific
- ventricular hypertrophy, pericardial effusion, ventricular aneurism can do this.
- effusions tend to form a globular outline, but LVH can do the same.
- LA enlargement straightens the left heart border
Clinical correllation is critical, eg tamponade.

Cardiac Failure
Kerley B lines, upper lobe diversion, cardiomegaly, pleural effusions, upper lobe diversion, parenchymal shadowing (Bat's wing).