Comment

On a film with diffuse increased pulmonary opacification you have to decide early on whether it is air space/consolidation or interstitial pattern shadowing. Air space shadowing has a number of characteristic features. It has poorly defined margins, a tendency to coalesce, produces air bronchograms and air alveolagrams. The causes of air space shadowing are extensive. If a chest X-ray simply shows a focal patch of consolidation and there are no further radiological clues or clinical history, it is often not possible to come to a single diagnosis.

In an examination or viva, a number of different types of air space shadowing films can be shown, e.g. ARDS with tubes and lines from ITU. Although time-consuming, it is important to check all tubes and lines for abnormal positioning. Look for rib fractures as a clue to contusion, renal dialysis double lumen lines, coronary care identification markers, etc. In these situations, it is possible to limit the differential diagnosis and then you must list the likely causes in reducing order of likelihood (Table 1.7).

Table 1.7 Causes of consolidation/air space shadowing

Infective exudate

Bacterial (Fig. 1.51)

Pneumococcus, Haemophilus, Legionella,

Klebsiella

TB (look at name)

Fungal

Histoplasmosis

Viral

Chickenpox

Influenza

Mycoplasma

Parasitic

Pneumocystis (although initially interstial

pattern)

Pulmonary oedema

Cardiogenic

Look for ECG leads, CCU label on ID (Fig. 1.52)

NB: in acute MI the heart size may be normal

Renal failure

Look for dialysis line, a double lumen central

line

Neurogenic

Noxious gas inhalation

Narcotics

Near drowning

Aspiration

Look for hiatus hernia, achalasia

Altitude

Aspirin OD

ARDS

ITU film, lines, ECG leads, intubation

Amniotic fluid/Fat embolus

Long bone fracture

Blood

Contusion

Rib fracture, other trauma

Pulmonary haemorrhage

Pulmonary infarct

Not strictly blood but fits best in this category

Malignant cells

Alveolar cell carcinoma

(Fig. 1.53)

Lymphoma

Choriocarcinoma mets

Others

Sarcoid

Loefflers

BOOP (Fig. 1.54)

PMF

Alveolar proteinosis

Radiation pneumonitis

Drugs

Amiodarone produces dense consolidation

Fig. 1.52 Focal pulmonary oedema. Acute mitral valve failure. This patient was on coronary care (admitted for acute myocardial infarction), and became suddenly short of breath. The heart is enlarged and there is a patch of air space shadowing in the right mid- and upper zone. This is caused by acute mitral regurgitation in the setting of papillary muscle rupture. The regurgitant jet is directed toward the right lung.

Fig. 1.52 Focal pulmonary oedema. Acute mitral valve failure. This patient was on coronary care (admitted for acute myocardial infarction), and became suddenly short of breath. The heart is enlarged and there is a patch of air space shadowing in the right mid- and upper zone. This is caused by acute mitral regurgitation in the setting of papillary muscle rupture. The regurgitant jet is directed toward the right lung.

Papillary Muscle Rupture NursingBoop Bronchiolitis Obliterans
Fig. 1.54 BOOP (bronchiolitis obliterans organising pneumonia). This CT is a fine example of why consolidation/air space shadowing causes air bronchograms. On a conventional chest X-ray, air bronchograms would be seen where the air-filled bronchi are surrounded by soft tissue.
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