Lower Lobe Atelectasis

Lower lobe atelectasis may be the initial imaging manifestation of lung cancer, and its detection on chest radiography and/or CT often allows the interpreting radiologist to be the first to suggest the diagnosis. Affected patients may be asymptomatic or present with vague complaints. Varying degrees of lower lobe atelectasis may occur due to other etiologies. Moderate and marked degrees of lobar atelectasis typically result in a triangular-shaped opacity with its apex oriented towards the hilum. Displaced interlobar fissures are a direct (primary) sign of atelectasis. A unique imaging feature of right lower lobe atelectasis is associated displacement of the minor fissure, in addition to the displaced major fissure that characteristically occurs in right or left lower lobe atelectasis.