The various faces of right upper lobe atelectasis.

The most common cause of RUL atelectasis in adults is neoplasm obstructing the RUL bronchus. Scarring of the lobe following chronic infection comes next. Other causes of obstruction, whether central or peripheral, are less common. The only direct sign of atelectasis is approximation of the fissures. All other signs are indirect. Increased density of the collapsed lobe is the most noticeable indirect sign. In the absence of adhesions the RUL is fixed at the hilum only. Therefore, it may take any one of the different shapes. Usually it is not difficult to recognize the dense shrunken lobe. Otherwise, we will have to depend on the other indirect signs, namely, displacement of mediastinal structures, elevation of the right hemidiaphragm, juxtaphrenic peak, elevation of hilum, "disappearance" of RUL artery, changes in position of of vascular (and bronchial) markings, and displacement of granuloma (if present).