 The hila may be difficult to assess on the frontal view, especially if both hila are slightly enlarged, since comparison with the opposite normal side is impossible. The lateral view may help. Most of the hilar densities are made up of the pulmonary arteries. Normally, no discrete mass is visible in the hila on the lateral view. When there is a hilar mass, such as might occur with enlargement of hilar lymph nodes, the hilum (or hila) will cast a distinct, lobulated masslike shadow on the lateral radiograph (Fig. 2-6). Figure 2-6 Hilar mass on lateral radiograph. Left lateral view of the chest shows a discrete lobulated mass in the region of the hila (solid black arrows). Normally, the hila do not cast a shadow that is easily detectable on the lateral projection. This patient had bilateral hilar adenopathy from sarcoidosis but any cause of hilar adenopathy or a primary tumor in the hilum would have a similar appearance. 来源：每天朗读一段医学影像学英语文章 |
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