What are the typical radiological findings in patients with Acute Respiratory Distress Syndrome (ARDS) on chest X-rays and Computed Tomography (CT) scans?

Radiological Findings in ARDS

Bilateral infiltrates on chest radiography are the hallmark radiological finding in ARDS, typically appearing as diffuse, bilateral, peripheral, and interstitial opacities, though they may present asymmetrically or in patchy, focal patterns. 1

Chest Radiography Findings

Classic Presentation

• Bilateral airspace opacification without evidence of fluid overload (no increased vascular pedicle width or cardiothoracic ratio) is the defining radiographic feature 1, 2
• The opacities are classically diffuse, bilateral, peripheral, and interstitial in distribution, though significant variation exists 1
• Asymmetric or patchy focal patterns are common and do not exclude the diagnosis 1

Important Limitations

• Standard chest radiographs are poor predictors of oxygenation severity or clinical outcome 1
• Early physiological changes in ARDS are often radiographically inapparent 1
• The radiographic findings associated with sepsis-induced ARDS vary widely in practice 1

Computed Tomography Findings

Primary CT Characteristics

• Bilateral, patchy, symmetric areas of ground-glass attenuation are the most characteristic CT finding 1
• Bilateral areas of airspace consolidation frequently accompany ground-glass opacities 1
• Predominantly subpleural distribution may be observed 1
• Dependent distribution of opacities occurs in most cases (86%) 3

Detailed CT Patterns

CT reveals more specific patterns than chest radiography:

• Opacities appear as patchy (42%), homogeneous (23%), ground-glass (8%), or mixed (27%) 3
• Basal regions are preferentially affected (68%) compared to hilar and apical regions 3
• Air bronchograms are frequently visible in areas of consolidation (89% of cases) 3

Additional CT Findings

• Pleural effusion occurs in approximately 50% of cases and does not worsen prognosis 3
• Pneumothorax develops in 32% of patients, typically loculated and anteromedial in location 3
• Pulmonary air cysts (30% of cases) are always multiple, mostly bilateral, and associated with higher mortality (55% vs 35% overall) 3

Comparative Diagnostic Value

CT Superiority Over Chest Radiography

• CT detects parenchymal disease in patients with normal chest radiographs 4
• CT provides additional clinically relevant information in 66% of cases, directly influencing treatment decisions in 22% 3
• CT has higher sensitivity than chest radiography for detecting pneumonia and ARDS-related changes 1

When to Use CT

• Consider CT when there is high clinical suspicion of ARDS with negative or indeterminate chest radiograph 1
• CT is particularly valuable for detecting complications such as ineffective thoracostomy tube positioning (detected in 13/20 patients) 3
• Quantitative CT analysis shows irreplaceable value in diagnosis, intervention evaluation, and prognostic prediction 5

Ultrasound Findings

Lung Ultrasound Characteristics

• Bilateral diffuse areas of reduced lung aeration with interstitial syndrome and consolidations 1
• Pleural line abnormalities and decreased lung sliding 1
• Pleural effusion may be present 1
• Absence of A-lines with confluent B-lines indicating poorly aerated lung 1

Clinical Utility

• Lung ultrasound is helpful for semi-quantitative evaluation of lung aeration and can guide respiratory intervention management 1
• Various ultrasound aeration scores can measure effects of fluid restriction, alveolar recruitment, and surfactant administration 1

Radiographic Assessment Tools

RALE Score

• The Radiographic Assessment of Lung Edema (RALE) score evaluates extent and density of alveolar opacities 6
• A RALE score cutoff of 10 provides 100% sensitivity and 71% specificity for ARDS diagnosis 6
• The score demonstrates excellent diagnostic accuracy (AUC 0.91) for ARDS 6
• Higher RALE scores correlate with ARDS presence (median 24 vs 6 in non-ARDS patients) 6

Common Pitfalls

• Do not exclude ARDS based on asymmetric or focal infiltrates – these patterns occur commonly 1
• Do not rely on chest radiography alone to assess severity – it correlates poorly with oxygenation defects 1
• Do not dismiss pleural effusion as a contraindication – it occurs in 50% of cases without worsening prognosis 3
• Monitor for pulmonary air cysts on CT – their presence significantly increases mortality risk 3