There is volume loss of the right upper lobe. The right upper zone has become dense due to lobar collapse. The volume loss has displaced the trachea which is PULLED to the right, and the horizontal fissure (arrow) has been PULLED upwards
Right upper lobe collapse is hardly ever caused by plugging of mucous or foreign bodies. The presence of right upper lobe collapse in an adult should therefore immediately raise the suspicion of an underlying malignant process occluding the right main bronchus.