The power of chest films: Evaluating lobar collapse

Lobar collapse (atelectasis) is characterized by loss of lung volume resulting from fibrosis, compression, surfactant abnormality, or bronchial obstruction. The prototypical form, resorption atelectasis, occurs when obstruction and the cycle of gas diffusion into the pulmonary capillaries render the affected segment partially or totally airless. The more atelectatic the lobe, the smaller and denser it appears on the chest film. Displacement of interlobar fissures is the only direct roentgenographic sign of lobar atelectasis; indirect signs arise from compensatory effects in the thorax. Malignancies, foreign bodies, secretions, and external compression are among the causes of bronchial occlusion leading to lobar collapse. It is important to rule out malignancy when the chest film finding is consistent with rounded atelectasis.