From the Guidelines
Yes, atelectasis can represent pneumonia.
Key Points
- Atelectasis can mimic pneumonia on radiographic images, making diagnosis challenging [ 1, 1 ].
- The presence of a new or progressive radiographic infiltrate plus at least two of three clinical features (fever, leukocytosis or leukopenia, and purulent secretions) is used to define pneumonia 1.
- However, atelectasis and other noninfectious processes can cause similar clinical findings, leading to potential misdiagnosis 1.
- Lung ultrasound can help differentiate between consolidations due to pulmonary embolism, pneumonia, or atelectasis 1.
- Certain chest radiograph findings, such as rapid cavitation of the pulmonary infiltrate or an air bronchogram, can be useful in establishing the diagnosis of pneumonia, but these findings are uncommon 1.
- Computed tomography (CT) scans may be more sensitive in detecting lung parenchymal changes, but may not provide sufficient diagnostic information to differentiate between causes of diffuse air-space shadowing 1.
From the Research
Atelectasis and Pneumonia
- Atelectasis can be mistaken for pneumonia on chest radiographs, particularly when pulmonary opacification is minimal or absent 2.
- The diagnosis of atelectatic pneumonia should be based on clinical signs and symptoms of pneumonia, as well as the identification of pathogenic bacteria, rather than radiographic identification of atelectasis alone 2.
- Differentiation between atelectasis and pneumonia can be challenging, and radiology and bronchoscopy may be necessary to identify the true nature of the etiology 3.
Diagnostic Challenges
- Clinical recognition of atelectasis can be difficult, and a high index of suspicion is needed to exclude atelectasis in children with respiratory tract symptomatology 3.
- The presence of atelectasis in children with pneumonia can be missed clinically, but can be diagnosed by radiological signs such as tracheal shift, elevated hemidiaphragm, and silhouette sign 3.
- Spectral-detector computed tomography (SDCT) parameters, such as iodine concentration and effective atomic number, can be used to differentiate between atelectasis and pneumonia on contrast-enhanced chest CT 4.
Quantitative Differentiation
- A threshold Hounsfield unit (HU) value can be used to distinguish pneumonia from atelectasis, with a sensitivity of 97% and specificity of 85% 5.
- The use of SDCT parameters, such as Ciodine and Zeff, can also differentiate atelectasis and pneumonia, but may not have added value compared to CT number measurement on conventional images 4.
- Contrast media is still needed for differentiation based on quantitative SDCT parameters 4.