NOTES:
Glossary Close

Atelectasis-Right Middle Lobe
Atelectasis is the loss of lung volume and therefore a direct sign is the displacement of interlobular fissures. Generally this is accompanied by increased density and possibly elevation of the hemidiaphragm, mediastinal displacement, or compensatory over-inflation. If there has been resorption of air within the atelectatic segment, there is generally an absence of air bronchograms. The pattern of the specific lobar or segmental collapse produces relatively specific findings on the chest film, often requiring both PA and lateral films for clear and specific definition.

PA (posterior-anterior) radiograph of this female patient (note breast shadows bilaterally) showed obscuration of the lower right cardiac border merging with opacification of the lung field underlying the right breast. Because the right middle lobe is immediately adjacent to the cardiac silhouette in that position collapse or opacification of the right middle lobe will merge densities between the lung and the heart and thus, the normal sharp boundary between heart and lung is lost. The lateral radiograph shows the triangular wedge of density that is characteristic of right middle lobe infiltrate. Note that the triangle has its apex superiorly and posteriorly. With atelectasis, the angle of that wedge will decrease and the right upper and lower lobes will overinflate slightly to compensate for loss of the right middle lobe volume.