helpsimple searchclear selectionselect all
Dictionary assisted search
All words
Any word/input
Exact phrase
in these
lexical topics:
  • Physics, Techniques and Procedures
  • Normal Anatomy
  • Musculoskeletal Imaging
  • Breast Imaging
  • Gastrointestinal Imaging
  • Urogenital Imaging
  • Chest Imaging
  • Cardiovascular Imaging
  • Neuroradiology
  • Head and Neck Imaging
  • Paediatric Imaging
 
 
 
Chest Imaging

Silicosis

a pneumoconiosis in which the predominant responsible dust is free silica which is present in many rocks. Exposed individuals work in quarries, drill or tunnel quartz-containing rocks, clean boilers or castings in iron and steel foundries or are exposed to sandblasting.

Basic lesions in silicosis are silicotic nodules which are predominantly located in the upper lung zones close to bronchioles and lymphatics with normal intervening lung parenchyma. They consist of scattered, relatively acellular, whirled, fibrous nodules containing silica particles. Silica in the peripheral zone of the nodules sets up further reactions resulting in enlargement of nodules and creation of new nodules. Fibrosis is more marked and more collagenous than that seen with other dusts, such as coal. Silicosis is often complicated by the development of large aggregates of confluent nodules matted together by fibrosis. These masses, which contain obliterated blood vessels and bronchi, may cavitate.

Silicosis usually takes many years to develop and an exposure of 10-20 years is usually necessary before the chest radiograph becomes abnormal. Early in the course of the disease small (1 - 2 mm) nodules are seen predominantly in the posterior portions of the upper and middle lung (Fig.1). As the process advances the nodules increase in size and become more widespread. The term progressive massive fibrosis is used when the silicotic nodules coalesce and masses greater than 1 cm in diameter develop. As these nodules coalesce, contraction of the upper lobes is seen and emphysematous changes occur surrounding these masses. These masses usually appear in the periphery of the lungs and can migrate slowly towards the hilus leaving emphysematous lung between the mass and the chest wall (Fig.2). When cavitation occurs airfluid levels can be seen. Associated hilar and mediastinal lymph node enlargement is common. A fairly typical feature is the development of eggshell-type calcifications in these nodes.

When exposure to silica is extremely intense a so-called acute silicosis or silicoproteinosis, can develop. In these cases, there is an alveolar proteinosis-like reaction in the air-spaces associated with abundant silica particles. This form is rare and usually the patient has worked as a sand blaster. Radiographically, there is widespread but predominant central and upper lung alveolar shadowing which progresses rapidly over a period of months. Prognosis is poor and death may ensue within 5 years of exposure.

 

JV

To view high resolution images,
please register first.

Click  here to register.

Already registered? Enter your e-mail in the window below.
Re-register

Fig.1

Chest radiograph showing multiple small nodules predominantly in the upper and middle zones.
Silicosis, Fig.1
Silicosis, Fig.2