What investigations should be ordered for a patient presenting with atelectasis?

Investigations for Atelectasis

Order a chest X-ray (both AP and lateral views) as the initial imaging study, followed by CT chest if the cause is unclear, if obstruction is suspected, or if the chest X-ray findings are equivocal.

Initial Imaging

• Chest radiography (AP and lateral projections) is mandatory to document the presence and location of atelectasis 1
• The lateral view is essential and should not be omitted, as it helps localize the affected segment or lobe 1
• Chest X-ray has limited sensitivity (58-64%) but remains the appropriate first-line test 2
• Look for direct signs: crowded pulmonary vessels, crowded air bronchograms, and displacement of interlobar fissures 3
• Look for indirect signs: pulmonary opacification, elevated diaphragm, mediastinal shift, hilar displacement, and compensatory hyperexpansion 3

When to Proceed to CT Imaging

CT chest should be performed when:

• The cause of atelectasis cannot be established with certainty on chest X-ray 4
• There is concern for obstructing tumor or mass (CT has 100% sensitivity vs 89% for plain radiography) 4
• You need to differentiate between benign and malignant causes of obstruction 5
• Bronchiectasis is clinically suspected (CT is the most specific test) 2
• There are persistent or recurrent symptoms despite treatment 2
• Multiple episodes of radiographically confirmed pneumonia have occurred 2

CT provides critical additional information:

• Precise location and extent of any obstructing process 5
• Differentiation between proximal obstructing tumor and collapsed lung (especially with IV contrast) 5
• Detection of mucus-filled bronchi within atelectatic lung (suggests obstruction) 4
• Absence of air bronchograms (favors obstructing tumor) 4

Additional Investigations Based on Clinical Context

Pulmonary function tests (PFTs):

• Consider when there are worsening respiratory symptoms or recurrent infections 2
• Include spirometry, lung volumes, and DLCO 2
• Note that PFTs can be normal even with ILD present, so they should not be used alone 2

Laboratory studies:

• CBC, CRP, blood gas analysis for base excess and lactate if sepsis or infection is suspected 2, 6
• These help differentiate infectious from non-infectious causes of fever when present 6

Bronchoscopy indications:

• Persistent mucous plugs requiring removal 1
• Suspected foreign body aspiration 7
• Need for bronchoalveolar lavage to obtain lower airway bacterial cultures 2
• Evaluation for tracheomalacia (ideally during spontaneous breathing) 2
• Suspected recurrent tracheoesophageal fistula 2
• When combined with upper endoscopy, helps assess for aspiration risk 2

Common Pitfalls to Avoid

• Do not assume atelectasis alone causes fever - this should be a diagnosis of exclusion, and other infectious causes must be ruled out first 6
• Do not rely on chest X-ray alone when obstruction is possible - CT has 0% false-negative rate for obstructing tumors vs 12% for plain films 4
• Do not order routine daily chest X-rays in stable ICU patients - only 6% show unexpected findings, and on-demand imaging is preferred 2
• Do not confuse atelectasis with lobar consolidation - this is a common clinical dilemma requiring careful radiographic interpretation 1