Special signs• Luftsichel sign: compensatory hyperinflation of the superior segment of the lower lobe in upper lobe collapse which herniates between the collapsed lobe and the mediastinum.• Juxtphrenic peak: a small triangular opacity near the dome of the diaphragm due to stretching of the inferior accessory fissure or inferior pulmonary ligament.• Broncholobar sign: A lobe collapses around the bronchus that enters it, so that if both the collapsed lobe & the bronchus are seen, they should be related to each other.
Entire lung collapseCauses:1. Obstruction of a main bronchus.2. Massive effusion.3. Massive pneumothorax.
Entire lung collapse with obstruction of a main bronchusPlain radiography:• Crowding of the broncho-vascular markings.• Increased lung density with absence of air bronchogram.• Diaphragmatic elevation.• Mediastinal shift.• Rib approximation.• Compensatory hyperinflation of the contralateral lung with retrosternal herniation in lateral radiograph.• Bronchial cutoff sign.
Entire lung collapse with massive pleural effusionPlain radiography:• Complete opacification of the ipsilateral hemithorax.• Mediastinal shift to the opposite side.CT with contrast:• The collapsed lung opacifies and appear denser than fluid in pleural space.• The collapsd lung appears tethered to the hilum.
Entire lung collapse with massive pneumothoraxPlain radiography:• Signs of pneumothorax.• The lung is tethered to the hilum.• There is no increase in lung density until collapse is complete and lung become airless (because of reduced perfusion associated with volume loss).
DD of complete opacification of a hemithorax (complete white out) Complete white out Trachea pulled Trachea central Trachea shifted Obstructive Consolidation Pleural Collapse (air bronchogram) effusion (bronchial cut off) Pneumonectomy Diaphragmatic(resected 5th / 6th rib) hernia
Segmental collapseDirect signs:1. Wedge shaped opacity with its apex at the hilum & its base in contact with the pleura.2. Fissure displacement.3. Silhouette sign.
Indirect signs:• Usually absent as the lost lung volume is small.
Right upper lung lobe anterior segmental atelectsis
Atypical patterns of collapse• Subsegmental atelectasis• Round collapse.
Round atelectasisDefinition:Folded lung due to fibrous adhesions between visceral & parietal pleura.Etiology:• After resolution of pleural effusion.• Asbestoses due to fibrosis of visceral & parietal pleura.
Pathogenesis:• Pleural effusion causes area of atelectasis of the compressed lobe the atelectatic lung tissue floats within the effusion when the effusion diminishes, the atelectatic lung tissue is tilted up or down the tilted lung tissue remains atelectatic and becomes engulfed by the visceral pleura of the remaining re-expanding lobe producing a mass that is formed of atelectatic lung tissue folded around thickened pleural indentations.
Location:• Posterior basal segment of the lower lobe (for mechanical reasons).
Plain radiography• Pleural based mass like density involving the lower lung zone.• Blunting of costo-phrenic angle.• Pleural thickening.• Pulmonary vasculature curving into the density (comet tail sign).
CT• Pleural based mass lesion associated with pleural thickening and converging bronchovascular markings (comet tail appearance).
MRI• The atelectatic lung has higher signal intensity than the adjacent pleural fluid on T1 WIs.• The atelectatic lung presents curved linear areas of low signal intensity correspond to the thickened indentations of the visceral pleura.
Obstructive Left upper lobe collapse 1. Veil-like opacification of the left hemithorax obscuring the left heart border. 2. The left hemidiaphragm is still visible - indicating sparing of the left lower lobe 3. Crowding of the left bronchovascular markings 4. Trachea deviated to the left. 5. Right heart border not visible - indicating mediastinal shift to the left 6. Volume loss of the left hemithorax 7. Luftsichel (air crescent) sign . 8. Ovoid density at the left hilum
Post-irradiation fibrosis 1. Trachea deviated. 2. No bronchial obstruction
Pleural effusion with compressive collapse of the left lung
Pleural effusion with underlying obstructive collapse
Combined RML & RLL collapseassociated with esophageal achalasia
• PA (Fig. A) and lateral (Fig. B) chest radiographs demonstrate two primary radiographic abnormalities of concern. The first is that of combined right middle lobe and right lower lobe atelectasis. The right hemithorax is relatively smaller in volume compared to the left from the underlying volume loss and there is ipsilateral mediastinal shift. Note the downward displacement of the horizontal fissure (single arrow) and right heart border silhouette from the middle lobe collapse. Notice also the downward displacement of the oblique fissure (double head right angle arrow), the small and inapparent right hilum and interlobar descending pulmonary artery, and silhouette of the diaphragm; cardinal signs of right lower lobe collapse. The second pertinent radiologic finding is a mottled, mixed density, mediastinal opacity, eccentric to the right, which extends from the T3 level to the hiatus. This mass displaces the trachea anteriorly and obliterates the retrotracheal triangle, retrocardiac clear space, and inferior hilar window consistent with a massively distended, fluid and debris-filled esophagus.