Study Syllabus for Classification of Radiographs of Pneumoconioses
Section 3: Pleural Abnormalities (Continued)
3C. Costophrenic Angle Obliteration
Costophrenic angle obliteration should not be confused with the normal muscle slip attachments of the diaphragm. It is of special relevance in asbestos-exposed people, but it frequently occurs, at least unilaterally, in those not exposed to asbestos or other dusts. Accordingly, minimal costophrenic angle blunting is not to be reported.
The ILO 2011D Standard Radiograph illustrating profusion subcategory 1/1 for small opacity t/t represents the lower limit of costophrenic angle obliteration that should be recorded. Therefore, the appearance of the right costophrenic angle seen in Radiograph #15C is not to be recorded, whereas that seen in Radiograph #15D is to be recorded.
If costophrenic angle obliteration is present, whether or not associated with diffuse pleural thickening of the chest wall or diaphragm, check R or L or both to indicate its anatomic distribution; if none is present, check “NO” and proceed to Section 4A. By convention, diffuse pleural thickening should be recorded in a hemithorax only in the presence of, and in continuity with obliteration of the costophrenic angle. If pleural thickening obliterates the costophrenic angle and involves the chest wall, the costophrenic angle obliteration and the upward extension of thickened pleura should each be classified as explained below (see Section 3D).
3D. Diffuse Pleural Thickening (Radiographs #18 to #19)
Diffuse pleural thickening is seen in many non-pneumoconiotic disease processes and likely represents thickening of the visceral pleura. Similar to plaque, diffuse pleural thickening may occur in profile or face on. The term “diffuse” indicates a homogeneous involvement to produce a “… general veiling of lung parenchymal detail”.
If diffuse pleural thickening is seen along the inner margin of the lateral chest wall in continuity with an obliterated costophrenic angle and as a homogeneous shadow, sharply outlined medially by adjacent lung, the thickening is then categorized as in profile. A minimum width of about 3 mm is required for in-profile diffuse pleural thickening to be recorded. On the frontal radiograph, diffuse pleural thickening involving the anterior chest wall may partially obscure lung detail or “veil” the lung. When this veiling is seen, the diffuse pleural thickening is categorized as face on.