5 Inhalational Lung Diseases and Pneumoconioses

Foreign Body Aspiration

Foreign body aspiration is typically seen in early childhood. Much less frequently, adults may inhale tooth fragments or dental fillings. Aspirated foreign bodies usually pass down the right main bronchus, which has a more vertical orientation than the left main bronchus. Radiographic features may indicate the presence and location of the foreign body (Figs. 5.1, 5.2). This can then be confirmed and removed at bronchoscopy or computed tomography (CT) may be performed prior to bronchoscopy.

Clinical Features

Aspiration material leads to tracheal/bronchial irritation with symptoms of cough and dyspnea. If the foreign body is not detected promptly, it becomes surrounded by fibrous tissue and patients then may be asymptomatic or have minimal symptoms for many years.

Radiologic Findings

Chest Radiograph

Radiopaque foreign bodies such as coins, marbles, and teeth are visible on standard radiographs. Indirect signs indicating the presence of a nonopaque foreign body include: (Figs. 5.3 and 5.4):

• Unilateral pulmonary lucency: This results from hyperinflation due to a check-valve obstruction and from reflex oligemia due to hypoventilation.
  
• Mediastinal shift: Air trapping in the affected lung leads to mediastinal shift to the contralateral side in expiration and a return to its normal position in inspiration.
  
• Lobar atelectasis and distal pneumonia develop when bronchial obstruction persists for at least several hours.

Fig. 5.1 Swallowed and aspirated teeth.

Fig. 5.2 Aspirated pin.

Fig. 5.3 Foreign body aspiration.

Fig. 5.4a, b Check-valve obstruction in foreign body aspiration (a) with contralateral shift of the mediastinum to the right side in expiration (b).

Computed Tomography

Helical CT will frequently allow direct visualization of the foreign body within the airway. Regional air trapping within the lung distal to the endobronchial body may be seen in cases of check-valve obstruction or atelectasis, and pneumonic consolidation may be present if the inhaled body leads to a high-grade obstruction.

Pneumoconiosis

• Shape and size of individual opacities: Small round opacities are classified by size as p, q, or r. Small irregular opacities are classified as s, t, or u (fine, medium, or coarse). Opacities greater than 1 cm in diameter are categorized as A, B, or C on the basis of their combined diameters (Fig. 5.5 and Table 5.1).
  
• Profusion of lesions in the pulmonary parenchyma (number of small opacities per lung zone) is graded on a scale of 0–3 (Fig. 5.5).
  
• Reactive pleural, pericardial, and hilar changes are described and coded.

Table 5.1 Pneumoconioses due to inorganic dusts (from Mathys 2001)

Fig. 5.5 Radiographic interpretation form based on the ILO Classification (see pp. 131–134 for coding and symbols).

The ILO provides three guidelines for interpreting radiographic findings:

• Standard reference radiographs (e. g., Fig. 5.6). Classification aided by standard reference radiographs helps to minimize interobserver variability.
  
• Verbal definitions (see text pp. 131–134).
  
• Drawings and diagrams (Figs. 5.5–5.9). These materials are the least reliable and should be used only to reinforce verbal descriptions and letter codes.

Formal disability assessment by a specially trained and approved physician is based strictly on use of standard reference radiographs, computer-interpretable data sheets, and in some cases CT assessment. A simplified scheme based on overall impression of pulmonary involvement has been adopted for clinical use. The predominant type of opacity and the predominant grade of profusion are determined using the ILO verbal definitions. For example, grade qq 2/2 refers to numerous round opacities, 1.5–3 mm in diameter, scattered throughout both lungs but not obscuring pulmonary vascular markings; qt 2/2 refers to the additional presence of irregular opacities 1.5–3 mm in diameter. This simplified scheme by definition precludes a detailed account of all findings and, in particular, of regional variations in severity of change.

Fig. 5.6 Illustrative radiographs from the ILO reference series.

Fig. 5.7 Diagram illustrating pulmonary opacity codes used in the ILO Classification. RUZ = right upper zone (see pp. 131–134, Fig. 2.10).