Atelectasis Workup

Updated: Dec 06, 2018
  • Author: Tarun Madappa, MD, MPH; Chief Editor: Nader Kamangar, MD, FACP, FCCP, FCCM  more...
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Workup

Laboratory Studies

Atelectasis of a significant size can result in hypoxemia as measured on arterial blood gas determinations. Arterial blood gas evaluation may demonstrate that despite a low PaO2. The PaCO2 level is usually normal but may be low as a result of the increased minute ventilation.

Atelectasis in the mechanically ventilated patient can result in the reduction of both dynamic and static compliance, and increased shunt physiology. [6] Complete left- or right-lung atelectasis in a mechanically ventilated patient can result in decreased lung compliance manifested by a decline in static compliance. Therefore, when monitoring peak and end-inspiratory plateau pressures, one should observe for a rise in both pressures.

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Imaging Studies

Chest radiographs and CT scans may demonstrate direct and indirect signs of lobar collapse. [7] Direct signs include displacement of fissures and opacification of the collapsed lobe.

Indirect signs include displacement of the hilum, mediastinal shift toward the side of collapse, loss of volume on ipsilateral hemithorax, elevation of ipsilateral diaphragm, crowding of the ribs, compensatory hyperlucency of the remaining lobes, and silhouetting of the diaphragm or the heart border.

Complete atelectasis of an entire lung (see images below) is when (1) complete collapse of a lung leads to opacification of the entire hemithorax and an ipsilateral shift of the mediastinum and (2) the mediastinal shift separates atelectasis from massive pleural effusion.

Complete atelectasis of the left lung. Mediastinal Complete atelectasis of the left lung. Mediastinal displacement, opacification, and loss of volume are present in the left hemithorax.
Complete right lung atelectasis. Complete right lung atelectasis.

With right upper lobe (RUL) collapse, the collapsed RUL shifts medially and superiorly, resulting in elevation of the right hilum and the minor fissure. Rarely, the RUL may collapse laterally, producing a masslike opacity that may look like a loculated pleural effusion. The minor fissure in RUL collapse is usually convex superiorly but may appear concave because of an underlying mass lesion. This is called the sign of Golden S. It is so named because this sign resembles a reverse S shape. It is created by a central mass obstructing the RUL bronchus and should raise suspicion for primary bronchogenic carcinoma, enlarged lymph nodes, or metastatic disease. Tenting of the diaphragmatic pleura juxtaphrenic peak is another helpful sign of RUL atelectasis. [8] Upon CT scanning, RUL collapse appears as a right paratracheal opacity, and the minor fissure appears concave laterally. Note the images below.

Atelectasis. Left upper lobe collapse showing opac Atelectasis. Left upper lobe collapse showing opacity contiguous to the aortic knob, a smaller left hemithorax, and a mediastinal shift.
Atelectasis. Right upper lobe collapse and consoli Atelectasis. Right upper lobe collapse and consolidation.
Atelectasis. Right upper lobe collapse. Atelectasis. Right upper lobe collapse.
Atelectasis. Chest posteroanterior radiograph demo Atelectasis. Chest posteroanterior radiograph demonstrates a right hilar bronchogenic carcinoma causing right upper lobe collapse with upward displacement of the minor fissure.
Atelectasis. Chest lateral radiograph demonstrates Atelectasis. Chest lateral radiograph demonstrates a right hilar bronchogenic carcinoma causing right upper lobe collapse with upward displacement of the minor fissure.
Atelectasis. CT scan of the chest shows tumor enca Atelectasis. CT scan of the chest shows tumor encasing and occluding the right upper lobe bronchus and collapse of the right upper lobe, with superior and medial displacement of the minor fissure.

Right middle lobe (RML) collapse (see images below) obscures the right heart border on a posteroanterior (PA) film. Occasionally, a triangular opacity may be observed. The lateral view demonstrates a triangular opacity overlying the heart because the major fissure shifts upward and the minor fissure shifts downward. Upon CT scanning, the atelectatic RML appears as a triangular opacity against the right heart border with the apex pointing laterally and is termed the "tilted ice cream cone sign."

Atelectasis. A lateral chest x-ray film confirms t Atelectasis. A lateral chest x-ray film confirms the diagnosis of right middle lobe collapse. The minor fissure moves down, and the major fissure moves up, leading to a wedge-shaped opacity.
Atelectasis. Left lower lobe collapse. Atelectasis. Left lower lobe collapse.
Atelectasis. Right middle lobe collapse showing ob Atelectasis. Right middle lobe collapse showing obliteration of the right heart border.
Atelectasis. Right middle lobe collapse on a later Atelectasis. Right middle lobe collapse on a lateral chest x-ray film.

In right lower lobe (RLL) collapse (see images below), the collapsed RLL shifts posteriorly and inferiorly. A triangular opacity obscuring the RLL pulmonary artery may be observed. The major fissure, which normally is not visible, is seen with RLL collapse. The superior mediastinal structure shifts to the right, causing a superior triangle sign. Laterally, the collapsed RLL blurs the posterior third of the right hemidiaphragm. Upon CT scanning, a paraspinal masslike appearance is observed. Concomitant RML and RLL atelectasis may appear as an elevated right hemidiaphragm or a subpulmonic effusion. An attempt to identify the fissures usually leads to the accurate diagnosis.

Atelectasis. Right lower lobe collapse. Atelectasis. Right lower lobe collapse.
Atelectasis. Both right lower lobe and right middl Atelectasis. Both right lower lobe and right middle lobe collapse. The left lung is hyperexpanded.
Atelectasis. The right lower lobe collapses inferi Atelectasis. The right lower lobe collapses inferiorly and posteriorly.
Atelectasis. Right lower lobe collapse without mid Atelectasis. Right lower lobe collapse without middle lobe collapse, the right major fissure is shifted downward and is now visible.

In left upper lobe (LUL) collapse (see images below), an atelectatic LUL shifts anteriorly and superiorly. In half the cases, a hyperexpanded superior segment of the left lower lobe (LLL) is positioned between the atelectatic upper lobe and the aortic arch. This gives the appearance of a crescent of the aerated lung, called the Luft Sichel sign. On lateral views, the major fissure is displaced anteriorly and the hyperexpanded RUL may herniate across the midline. On PA views, an atelectatic LUL produces a faint opacity in the left upper hemithorax, obliterating the left heart border. A CT scan demonstrates the inferior location of the collapsed lobe and the shift of the RUL across the midline.

Atelectasis. Left upper lobe collapse showing opac Atelectasis. Left upper lobe collapse showing opacity contiguous to the aortic knob, a smaller left hemithorax, and a mediastinal shift.
Atelectasis. CT scan of a left upper lobe collapse Atelectasis. CT scan of a left upper lobe collapse with a small pleural effusion.
Atelectasis. The left upper lobe collapses anterio Atelectasis. The left upper lobe collapses anteriorly on a lateral chest x-ray film.
Atelectasis. Left upper lobe collapse. The top of Atelectasis. Left upper lobe collapse. The top of the aortic knob sign is demonstrated.
Atelectasis. Left upper lobe collapse. The Luft Si Atelectasis. Left upper lobe collapse. The Luft Sichel sign is demonstrated clearly in this radiograph.
Atelectasis. Chest CT scan showing left upper lobe Atelectasis. Chest CT scan showing left upper lobe collapse.

In left lower lobe (LLL) collapse (see images below), increased retrocardiac opacity silhouettes the LLL pulmonary artery and the left hemidiaphragm on frontal views. The hilum shifts downward, and the rotation of the heart produces flattening of the cardiac waist, which is known as the flat-waist sign. The superior mediastinum may shift and obliterate the aortic arch, the top of the aortic-knob sign. On lateral radiographs, opacity makes the posterior third of the left diaphragm indistinct. A CT scan shows the atelectatic LLL in the inferior posterior location.

Atelectasis. Loss of volume on the left side; an e Atelectasis. Loss of volume on the left side; an elevated and silhouetted left diaphragm; and an opacity behind the heart, called a sail sign, are present.
Atelectasis. Left lower lobe collapse. Atelectasis. Left lower lobe collapse.
Atelectasis. Left lower lobe collapse. The sail si Atelectasis. Left lower lobe collapse. The sail sign is obvious.
Atelectasis. Left lower lobe collapse on posteroan Atelectasis. Left lower lobe collapse on posteroanterior view.

Rounded atelectasis is a segmental or subsegmental atelectasis that occurs secondary to visceral pleural thickening and entrapment of lung tissue. Rounded atelectasis is usually located in the lower lobes, the lingula, or the RML. On chest radiographs, rounded atelectasis manifests as a subpleural mass, with bronchovascular structures projecting out of the mass toward the hilum. An associated parietal pleural plaque may be present. The swirl appearance of bronchovascular shadows is called the comet-tail sign. [9]

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Procedures

Flexible fiberoptic bronchoscopy can be a useful diagnostic and therapeutic procedure. Bronchoscopy helps evaluate the cause of bronchial obstruction. In addition, bronchoscopy helps clear mucous plugs when they cause bronchial obstruction. Bronchoscopy has limitations. Because only the subsegmental bronchi are visualized, a distal endobronchial lesion is not accessible through bronchoscopy.

In an evaluation of middle lobe syndrome, bronchoscopy may show an endobronchial etiology (mucus plugging/broncholithiasis/tumor), although inflammatory processes and defects in the bronchial anatomy and collateral ventilation have been designated as the nonobstructive causes of the syndrome.

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Histologic Findings

During fiberoptic bronchoscopy, the washing, brushing, and biopsy specimens of any obstructing mass should be examined for evidence of malignancy or Aspergillus mucous plugging (ie, allergic bronchopulmonary aspergillosis).

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