Pulmonary emphysema on chest radiography

Main radiological signs

In chronic obstructive pulmonary disease (COPD), initial chest radiograph findings may be absent. However, as emphysema progresses, a number of characteristic symptoms appear:

• Hyperinflation (overexpansion of lung tissue).
• Oligemia — visual depletion of the pulmonary (vascular) pattern.
• Bronchial changes — thickening of their walls, producing ring-like and tubular shadows.
• "Dirty chest" sign (dirty chest) — a consequence of enhanced linear markings and blurred vessel contours.
• Sabre-sheath trachea (sabre-sheath trachea).

Patients with severe hypoxia may develop cor pulmonale (cor pulmonale). In this case, the radiograph shows cardiomegaly, widening of the pulmonary hila, and enlargement of intermediate segmental vessels.

Signs of hyperinflation

The degree of hyperinflation correlates reliably with the presence and severity of the emphysematous process. Key criteria for lung overinflation include:

1. The vertical dimension of the right lung exceeds 29.9 cm.
2. The right dome of the diaphragm is depressed to the level of the anterior segment of the 7th rib or lower.
3. Flattening of the diaphragmatic dome.
4. Widening of the costophrenic angle.
5. Narrowing of the transverse cardiac silhouette.
6. Increase of the retrosternal space on the lateral radiograph.

In areas unaffected by emphysema, vessel caliber may remain normal or show compensatory enlargement. In affected areas, vessels are displaced by bullae, their branching angles are widened, and side branches are lost.

Note: If left ventricular failure joins or cor pulmonale develops, the radiological picture is distorted: the heart enlarges, the diaphragm becomes less flat, and vessels appear thickened.

Bullae and vanishing lung syndrome

Bullae are air-filled spaces measuring 1 cm or more, which can reach the volume of an entire hemithorax. They frequently cause compressive (relaxation) atelectasis of the adjacent healthy lung tissue. The walls of bullae are very thin and sometimes entirely invisible on radiographs. In the paraseptal type, they tend to locate in the upper regions, while in the panlobular type, they are distributed more evenly.

A special form is giant bullous emphysema (primary bullous disease of the lung, or vanishing lung syndrome). It is typical for young men. Huge bullae form predominantly in the upper lobes, appearing as areas of increased radiolucency without vascular markings, bounded by a thin wall. They are capable of compressing the adjacent lung and even herniating across the anterior mediastinum to the healthy side.

Severe complications are associated with bullae. Their rupture (especially at the apices) often leads to spontaneous pneumothorax. With hemorrhage or infection within the cavity, a horizontal fluid level may appear, and wall thickening of an infected bulla makes it look like an abscess. If the wall of a bulla thickens unevenly, a mural nodule appears, or its diameter changes, the development of carcinoma should be suspected.

CT presentation and visual patterns

Multidetector computed tomography (HRCT) is the gold standard for assessing emphysema and phenotyping COPD.

According to the Fleischner Society classification, three main subtypes are distinguished:

• Centrilobular emphysema: localized areas of decreased attenuation (low-density areas) without visible walls against a background of healthy lung tissue. The upper lobes are more frequently affected.
• Panlobular emphysema: the most severe variant, predominantly involving the basal regions (characteristic of $\alpha_1$-antitrypsin deficiency).
• Paraseptal emphysema: changes are localized in the periphery, frequently combined with bullae.

In addition to parenchymal destruction itself, CT allows for quantitative and visual assessment of bronchial wall thickening, signs of small airway disease, and expiratory air trapping (on expiratory scans).

Class and exam questions

What else to study on this topic

• Quantitative CT in COPD (fSAD assessment)
• Congenital lobar overinflation and bronchial atresia
• Bronchiolitis obliterans and mosaic perfusion
• Radiological presentation of asthma
• Vanishing lung syndrome

Other topics in the «Chest Radiology» section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.