Upper and Middle Lobe Atelectasis

Abstract

Upper and middle lobe atelectasis discusses the radiographic and computed tomography (CT) manifestations of upper and middle lobe atelectasis. The most common radiographic signs of right upper lobe atelectasis include upward and medial displacement of the minor fissure, superior displacement of adjacent structures such as the hilum and main bronchus, and ipsilateral shift of the mediastinal structures. The S sign of Golden results from a centrally obstructing lung cancer as the cause of the atelectasis and manifests as a reverse S configuration of the minor fissure outlined by atelectatic lung and central mass. Left upper lobe atelectasis manifests with a veil-like opacity on frontal radiography with leftward shift of upper mediastinal structures such as the trachea and upward shift of the left main bronchus and left hemidiaphragm. The Luftsichel sign or air crescent sign may be seen and represents the hyperexpanded superior segment of the left lower lobe outlining the transverse aortic arch. Lobar atelectasis in the inpatient setting is most commonly secondary to an obstructing mucus plug. Lobar atelectasis in the outpatient setting is often a heralding sign of a centrally obstructing lung cancer and should be further evaluated with contrast-enhanced CT and/or bronchoscopy.