Combined lobar atelectasis of the right lung: imaging findings.

Combined lobar atelectasis refers to the condition in which the volumes of two lobes of the lung are decreased simultaneously. Because the right lung has three lobes, three combinations of combined atelectasis are possible. The most frequent combination is that of middle and lower lobar atelectasis caused by obstruction of the bronchus intermedius [1,2]. Combined atelectasis of the upper and middle lobes is uncommon, although it occurs more frequently than anticipated [1]. The least common combination is that of right upper and lower lobe atelectasis. Awareness of the radiographic and CT findings of combined lobar atelectasis of the right lung is important in making the correct diagnosis. In this pictorial essay, we illustrate the spectrum of radiographic and CT features of this condition.