The Pneumoconioses

Chapter 8 The Pneumoconioses



Many respiratory disorders can be occupationally induced. The most important of these are the pneumoconioses. A pneumoconiosis is a diagnosable disease produced by the inhalation of dust (i.e., particulate matter in the solid phase, excluding living organisms). Mineral dust can be classified as fibrogenic, such as asbestos and silica, or inert, such as iron, tin, or barium. The metal dusts include beryllium and cobalt, which are associated with granulomatous pneumonitis and giant cell pneumonitis, respectively (Table 8-1). Most pneumoconioses produce diffuse opacities on the chest radiograph that are similar to those seen in other interstitial lung disorders.


Table 8-1 Dust Diseases























Agent Examples Disorders
Mineral dusts Asbestos
Silica
Coal
Pneumoconioses
Metal dusts Iron
Tin
Barium
“Inert dust” pneumoconioses
Metal dusts Beryllium
Cobalt
Granulomatous pneumonitis
Giant cell pneumonitis
Biologic dusts Spores
Mycelia
Bird droppings
Hypersensitivity pneumonitis (allergic alveolitis)


INTERNATIONAL LABOUR ORGANIZATION CLASSIFICATION OF PNEUMOCONIOSES


The International Labour Organization (ILO) classification of the radiographic appearances of the pneumoconioses is a standardized, internationally accepted system used to codify the radiographic changes in the pneumoconioses in a reproducible manner (Box 8-1). The advantage of the system is that it provides graphic and morphometric terms to describe diffuse lung patterns. The classification includes conventions of small, rounded (nodules) and small, irregular (linear and reticular) opacities (Fig. 8-1). The small, rounded opacities are classified according to the approximate diameter of the predominant opacity: p (up to 1.5 mm in diameter), q (1.5 to 3 mm in diameter), and r (3 to 10 mm in diameter). Small, irregular opacities are classified on the basis of thickness and appearance: s (fine, up to 1.5 mm thick), t (medium, 1.5 to 3 mm thick), and u (coarse or blotchy, 3 to 10 mm thick).




The ILO scheme also quantifies the radiographic severity, or profusion, on a 12-point scale. There are four basic categories: 0, normal; 1, slight; 2, moderate; and 3, advanced. The distribution and extent of opacities are recorded in six zones. The convention for large opacities describes the conglomerate masses identified in some of the pneumoconioses. The 1980 ILO classification also includes detailed categorization of pleural thickening that is quantified and classified as diffuse or circumscribed (i.e., plaque).



SILICOSIS




Simple Silicosis


Simple silicosis (Box 8-3) has no symptoms and is not associated with any significant changes in pulmonary function.







Complicated Silicosis




Radiographic Findings


On the chest radiograph, the opacities of complicated silicosis appear in the middle zone or in the periphery of the lung in the upper lobes (Fig. 8-4A). They tend to migrate to the hilum, leaving overinflated emphysematous lung tissue in the surrounding lung, particularly at the bases. The more extensive the progressive massive fibrosis, the less the apparent the nodularity in the remaining lungs.



As conglomeration develops, the lungs gradually lose volume, and cavitation of the masses may result from ischemic necrosis. In this setting, tuberculosis or infection with atypical mycobacteria may supervene. Superimposed tuberculosis may be difficult to detect radiographically; findings such as cavitation of conglomerate masses, pleural reaction at the apices, or other rapid radiographic changes are suggestive (Fig. 8-5). The diagnosis of supervening tuberculosis, however, is bacteriologic rather than radiologic.





Accelerated Silicosis and Acute Silicosis






COAL WORKER’S PNEUMOCONIOSIS


Coal worker’s pneumoconiosis is a compensable occupational disease in the United States. This disease is particularly common in underground miners. In studies of coal worker’s pneumoconiosis in this population, prevalences between 9% and 27% have been reported.



Simple Coal Worker’s Pneumoconiosis




Feb 28, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on The Pneumoconioses
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