Abnormal Pulmonary Shadows

Air-Bronchogram Sign

If bronchi have fluid then you will not be able to see Air Bronchogram Sign. Bronchogram Sign is “+” for:
Pneumonia
Pulmonary Edema
Pulmonary Infarcts
Certain chronic lung diseases

Air bronchogram sign (only useful when alveoli are filled with fluid which contrasts with air in the bronchi).

Abnormal Intrapulmonary Shadows Categories of Observation

1. Air-space filling
Pulmonary edema
Pulmonary consolidation (alveolar infiltrates) with or without atelectasis
2. Spherical shadows
3. Line shadows
4. Wide-spread small shadows

Presence of cavitations or calcifications should be noted.

1. Air-Space Filling Shadows – replacement of air in alveoli either by fluid or other materials

Transudate (pulmonary edema)
Replacement of air in alveoli either by fluid or other materials
Exudate (infection, infarction, pulmonary contusion, hemorrhage, collagen disease, allergy)
Shadow with ill-defined border (except when in contact with fissure)

Silhouette Sign

The bronchi are pulmonary structures. Visualization of bronchi denotes pulmonary lesion. This excludes the mediastinal area and the pleural cavity.
1a. Pulmonary Edema
A. Interstitial
B. Alveolar (always acute)
Since edema initially collects in interstitial tissues, all patients with alveolar edema also has interstitial.

Interstitial (Line Shadows)

Means line is traversing the lung
All line shadows except fissures and vessels are abnormal
indicate significant disease
Septal Lines – seen in Interstitial Pulmonary Edema
Pulmonary Septa – connective tissue planes containing lymph vessels Kerly A:
Radiate towards hilum in mid and upper zones thinner than blood vessels do not reach edge
Cause
Left ventricular failure Kerly B: Horizontal
Never more than 2cm in length
Seen best in periphery of lung bases – usually around costophrenic angle Causes
Pulmonary edema
Lymphangitis carcinomatosis (blockage of pulmonary lymph by cancerous tissue)

B. Alveolar Edema
Most common causes:
Left ventrical failure
Renal failure
Over-transfusion Visually – always acute Almost always bilateral Involves all lobes
Shadowing increases at hilum and fades away toward periphery (butterfly/bat wing edema)
Edema is distinguishable from exudates in rapidity of appearance and speed of disappearance on treatment.
1B. Pulmonary Consolidation (alveolar Infiltrates) and Collapse
Often coexists
Consolidation of Lobe
Diagnostic of bacterial pneumonia
Requires knowledge of anatomy of lobes
Visually; Opaque (white) lobe (except for air in bronchi-bronchogram)