The Roentgen Appearance of Lobar and Segmental Collapse of the Lung

Abstract

Collapse of a single lobe of the lung is most frequently misinterpreted when it occurs in one of the upper lobes. It is confused with a localized area of consolidation, a mediastinal tumor, or an aortic aneurysm, and in some instances, especially in the presence of a long standing fibrotic process without apparent atelectasis, it may be completely overlooked. Its occurrence is relatively infrequent as compared with collapse in the lower lobes or the middle lobe, but it is common enough to warrant greater emphasis than has been given it in the literature. In the group of 600 cases forming the basis of this study,2 the upper lobes were involved in 95, or 16 per cent. Certain roentgenologic signs which characterize collapse of an upper lobe and which, if recognized, will lessen some of the confusion regarding its diagnosis will be described. It has been noted in earlier papers of this series that in the majority of instances it is possible with satisfactory technic to demonstrate the septa which bound the individual lobes of the lung. These lines, which roentgenologically can be thought of as partitions between the various lobes, are seen to best advantage on the lateral roentgenogram. The routine postero-anterior view is depended upon to show any abnormal shadow of increased density, the presence and degree of emphysema in the adjoining lobes, the position of the trachea and upper mediastinum, the relative planes in which the hili are located, and usually the minor septum. The upper lobes lie superiorly and anteriorly in the chest; that is, the left upper lobe is anterior to the major septum along its entire course, while the right upper lobe lies above the minor septum and anterior to that portion of the major septum above its junction with the minor septum. The location of a normal lobe in relation to the septa is stressed repeatedly because of its diagnostic significance. By the recognition of the individual lobes and the septa which bound them, it becomes more nearly possible to demonstrate on a roentgenogram the precise unit of a lung that is projected on a given area. In this way, it is possible roentgenologically to recognize the presence of a pulmonary unit which is not assuming its full share in aeration even before an abnormal shadow of increased density, indicating the nature of the disease process (or in some instances its result) can be detected. The significance of this concept is similar to that of a break in the peristaltic wave in the stomach pointing to a neoplasm or ulcer crater which otherwise might be overlooked. With a few exceptions, the roentgen appearance of collapse of an upper lobe or of its segments is essentially the same regardless of the side involved. On the left, the lingula of the upper lobe occupies a position in the chest similar to that of the middle lobe on the right, but it derives its bronchial supply from the left upper lobe bronchus and is not separated from the remainder of the upper lobe by a fissure.