Criteria for the radiographic diagnosis of emphysema
| View | Sign |
| Posteroanterior | Depression and flattening of the diaphragm with blunting of costophrenic angles. The actual level of the diaphragm is not as significant as the contour. The bodybuild of the subject should also be considered. In a short stocky subject, this sign might be positive even if the diaphragm was at the level of the 10th rib posteriorly. |
| Irregular radiolucency of the lung fields. This manifestation is the result of the irregularity in distribution of the emphysematous tissue destruction. | |
| Lateral | Abnormal retrosternal space. This is defined as a space showing increased radiolucency and measuring ≥2.5 cm from the sternum to the most anterior margin of the ascending aorta. |
| Flattening or even concavity of diaphragmatic contours. A useful index of this change is the presence of a ≥90° sternodiaphragmatic angle. In most patients with emphysema, this junction is more readily seen than in subjects with normal chests. |
Emphysema is considered to be present if the chest radiographs reveal any two or more of the above criteria 8. Sometimes, it may not be clear not a particular diaphragmatic contour is flat. A useful way of resolving this in the posteroanterior radiograph is to determine the straight line from the costophrenic junction to the vertebrophrenic junction on each side. If the highest level of the diaphragmatic contour is <1.5 cm above this line, the diaphragm may be recorded as flat. The same dimension can be used in the lateral radiograph, measuring from a line connecting the costophrenic junction posteriorly to the sternophrenic junction anteriorly 9. Flattening of the diaphragmatic contours with blunting of costophrenic and sternophrenic angles are seldom, if ever, seen under conditions of acute lung hyperinflation. In addition, areas of irregular radiolucency of the lung fields are absent in such conditions 9.