Lung atelectasis
Updates to Article Attributes
Lung atelectasis (plural: atelectases) refers to collapse or incomplete expansion of pulmonary parenchyma.
Terminology
Atelectasis may be used synonymously with collapse, but some authors reserve the term "atelectasis" for partial collapse, not inclusive of total atelectasis of the affected part of lung or of whole lung collapse.
Classification
Atelectasis is a radiopathological sign which can be classified in many ways. The aim of each classification approach is to help identify possible underlying causes together with other accompanying radiological and clinical findings.
Atelectasis can be subcategorised based on underlying mechanism, as follows:
-
resorptive (obstructive) atelectasis
- occurs as a result of complete obstruction of an airway
- no new air can enter the portion of the lung distal to the obstruction and any air that is already there is eventually absorbed into the pulmonary capillary system, leaving a collapsed section of the affected lung
- because the visceral and parietal pleura do not separate in resorptive atelectasis, traction is created, and if the loss of volume is considerable, mobile thoracic structures may be pulled toward the side of volume loss ("mediastinal shift")
- potential causes of resorptive atelectasis include obstructing neoplasms, mucus plugging in asthmatics or critically ill patients and foreign body aspiration
- resorptive atelectasis of an entire lung ("collapsed lung") can result from complete obstruction of the right or left main bronchus
-
passive (relaxation) atelectasis
- occurs when contact between the parietal and visceral pleura is disrupted
- the three most common specific aetiologies of passive atelectasis are pleural effusion, pneumothorax and diaphragmatic abnormality
-
compressive atelectasis
- occurs as a result of any thoracic space-occupying lesion compressing the lung and forcing air out of the alveoli
-
cicatrisation atelectasis
- occurs as a result of scarring or fibrosis that reduces lung expansion
- common aetiologies include granulomatous disease, necrotising pneumonia and radiation fibrosis
-
adhesive atelectasis
- occurs from surfactant deficiency 2
- depending on aetiology, this deficiency may either be diffuse throughout the lungs or localised
-
gravity dependant atelectasis (dependent atelectasis)
- in the most dependent portions of the lungs due to the weight of the lungs
- osteophyte-induced adjacent pulmonary atelectasis and fibrosis
Atelectasis can also be subcategorised by morphology as follows:
-
linear
(plate(a.k.a. plate, band, discoid, subsegmental) atelectasis) atelectasis: a minimal degree of collapse as seen in patients who are not taking deep breaths ("splinting"), such as postoperative patients or patients with rib fracture or pleuritic chest pain; this is very common - round atelectasis: classically associated with asbestos exposure
or by anatomical extent:
- lung atelectasis: complete collapse of one lung
- lobar atelectasis: collapse of one or more lobes of a lung.
- segmental atelectasis: collapse of one or more individual pulmonary segments
-
round atelectasis: classically associated with asbestos exposure. osteophyte induced adjacent pulmonary atelectasis
Radiographic features
Vary depending on the underlying mechanism and fibrosistype of atelectasis
Plain radiograph / CT
Direct signs of atelectasis
displacement of interlobar fissurescrowding together of pulmonary vesselscrowded air bronchograms (does not apply to all types of atelectasis; can be seen in subsegmental atelectasis due to small peripheral bronchi obstruction, usually by secretions; if the cause of the atelectasis is central bronchial obstruction, there will usually be no air bronchograms)
Indirect signs of atelectasis
pulmonary opacificationshifting granuloma (or any other previously documented lesion, used as a reference for comparison)compensatory hyperexpansion of the surrounding or contralateral lungdisplacement of the heart, mediastinum, trachea, hilumelevation of the diaphragmpropinquity of the ribs
Resorptive (obstructive) atelectasis
increased density (opacity) of the atelectatic portion of lungdisplacement of the fissures toward the area of atelectasisupward displacement of hemidiaphragm ipsilateral to the side of atelectasiscrowding of pulmonary vessels and bronchi in region of atelectasis+/- compensatory overinflation of unaffected lung+/- displacement of thoracic structures (if atelectasis is substantial)
Linear (plate, discoid, subsegmental) atelectasis
relatively thin, linear densities in the lung bases oriented parallel to the diaphragm (known as Fleischner lines)
Ultrasound
The sonographic morphology of atelectatic lung may resemble hepatic parenchyma, often referred to as "tissue-like" or "hepatized" in appearance. Distinguishing features of atelectasis by etiology may appear as follows:
-
compressive atelectasis is most often visualized in the costophrenic recess bordered by a disproportionately large pleural effusion-
low-level, homogenous echogenicity with few to noair bronchograms -
margins are usually regular with a triangular shape10 -
ashred signmay be present at the transition to aerated lung
-
-
obstructive atelectasisearly static air bronchograms due to distal air trapping-
as the air is resorbed, bronchi may fill with fluid resulting in anechoic, tubular structures known asfluid bronchograms11 -
may be differentiated from blood vessels withcolor flow Doppler
History and etymology
Atelectasis comes from the Greek words ateles and ektasis translating to 'incomplete stretching or expansion'.
Radiographic features
Vary depending on the underlying mechanism and type of atelectasis
Plain radiograph / CT
Direct signs of atelectasis
displacement of interlobar fissurescrowding together of pulmonary vesselscrowded air bronchograms (does not apply to all types of atelectasis; can be seen in subsegmental atelectasis due to small peripheral bronchi obstruction, usually by secretions; if the cause of the atelectasis is central bronchial obstruction, there will usually be no air bronchograms)
Indirect signs of atelectasis
pulmonary opacificationshifting granuloma (or any other previously documented lesion, used as a reference for comparison)compensatory hyperexpansion of the surrounding or contralateral lungdisplacement of the heart, mediastinum, trachea, hilumelevation of the diaphragmpropinquity of the ribs
Resorptive (obstructive) atelectasis
increased density (opacity) of the atelectatic portion of lungdisplacement of the fissures toward the area of atelectasisupward displacement of hemidiaphragm ipsilateral to the side of atelectasiscrowding of pulmonary vessels and bronchi in region of atelectasis+/- compensatory overinflation of unaffected lung+/- displacement of thoracic structures (if atelectasis is substantial)
Linear (plate, discoid, subsegmental) atelectasis
relatively thin, linear densities in the lung bases oriented parallel to the diaphragm (known as Fleischner lines)
Ultrasound
The sonographic morphology of atelectatic lung may resemble hepatic parenchyma, often referred to as "tissue-like" or "hepatized" in appearance. Distinguishing features of atelectasis by etiology may appear as follows:
-
compressive atelectasis is most often visualized in the costophrenic recess bordered by a disproportionately large pleural effusion-
low-level, homogenous echogenicity with few to noair bronchograms -
margins are usually regular with a triangular shape10 -
ashred signmay be present at the transition to aerated lung
-
-
obstructive atelectasisearly static air bronchograms due to distal air trapping-
as the air is resorbed, bronchi may fill with fluid resulting in anechoic, tubular structures known asfluid bronchograms11 -
may be differentiated from blood vessels withcolor flow Doppler
History and etymology
Atelectasis comes from the Greek words ateles and ektasis translating to 'incomplete stretching or expansion'.
-</ul><p>Atelectasis can also be subcategorised by <strong>morphology</strong> as follows: </p><ul>- +<li><a href="/articles/osteophyte-induced-adjacent-pulmonary-atelectasis-and-fibrosis">osteophyte-induced adjacent pulmonary atelectasis and fibrosis</a></li>
- +</ul><p>Atelectasis can also be subcategorised by <strong>morphology</strong>: </p><ul>
-<a href="/articles/linear-atelectasis">linear (plate, band, discoid, subsegmental) atelectasis</a>: a minimal degree of collapse as seen in patients who are not taking deep breaths ("splinting"), such as postoperative patients or patients with rib fracture or pleuritic chest pain; this is very common</li>- +<a title="Linear atelectasis" href="/articles/linear-atelectasis">linear (a.k.a. plate, band, discoid) atelectasis</a>: a minimal degree of collapse as seen in patients who are not taking deep breaths ("splinting"), such as postoperative patients or patients with rib fracture or pleuritic chest pain; this is very common</li>
- +<li>
- +<a href="/articles/round-atelectasis">round atelectasis</a>: classically associated with asbestos exposure</li>
- +</ul><p>or by <strong>anatomical</strong> extent:</p><ul>
- +<li>lung atelectasis: complete collapse of one lung</li>
-<a href="/articles/segmental-atelectasis">segmental atelectasis</a>: collapse of one or more individual pulmonary segments<ul><li><a href="/articles/subsegmental-atelectasis">subsegmental atelectasis</a></li></ul>- +<a href="/articles/segmental-atelectasis">segmental atelectasis</a>: collapse of one or more individual pulmonary segments<ul><li><a title="Subsegmental atelectasis" href="/articles/subsegmental-atelectasis">subsegmental atelectasis</a></li></ul>
-<li>-<a href="/articles/round-atelectasis">round atelectasis</a>: classically associated with asbestos exposure.</li>-<li><a href="/articles/osteophyte-induced-adjacent-pulmonary-atelectasis-and-fibrosis">osteophyte induced adjacent pulmonary atelectasis and fibrosis</a></li>-</ul><h4>Radiographic features</h4><p>Vary depending on the underlying mechanism and type of atelectasis</p><h5>Plain radiograph / CT</h5><p><!--[if gte mso 9]><xml>- +</ul><p><strong style="font-size:1.5em; font-weight:bold">Radiographic features</strong></p><p>Vary depending on the underlying mechanism and type of atelectasis</p><h5>Plain radiograph / CT</h5><p><!--[if gte mso 9]><xml>
-</ul><h4>History and etymology</h4><p>Atelectasis comes from the Greek words <em>ateles</em> and <em>ektasis</em> translating to 'incomplete stretching or expansion'.</p>- +</ul><h4>History and etymology</h4><p>Atelectasis comes from the Greek words 'ateles' and 'ektasis' translating to 'incomplete stretching or expansion'.</p>