Peripheral (Subpleural) Lung Disease Distribution
Jonathan H. Chung, MD
DIFFERENTIAL DIAGNOSIS
Common
Pneumonia
Lung Cancer
Rounded Atelectasis
Septic Emboli
Pulmonary Contusions
Less Common
Pulmonary Infarction
Cryptogenic Organizing Pneumonia
Chronic Eosinophilic Pneumonia
Usual Interstitial Pneumonitis
Desquamative Interstitial Pneumonia
Rare but Important
Amyloidosis
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
Acute vs. chronic
Acute abnormalities
Pneumonia
Septic emboli
Pulmonary infarctions (within 12-24 hours of embolic event); slow resolution
Chronic abnormalities
Lung cancer
Round atelectasis
Cryptogenic organizing pneumonia
Chronic eosinophilic pneumonia
Chronic interstitial lung diseases
Helpful Clues for Common Diagnoses
Pneumonia
Airspace opacities: Ground-glass opacities to dense consolidation
Reactive lymphadenopathy; very large lymph nodes unusual
Parapneumonic pleural effusion or empyema
Correlation with sputum, WBC count, and clinical presentation paramount
Lung Cancer
Suggestive findings include
Focal mass-like consolidation larger than 3 cm
Spiculated margins
Thick-walled or nodular cavitation
Large hilar &/or mediastinal lymphadenopathy (> 2 cm)
Concomitant emphysema and smoking history
Rounded Atelectasis
Definitive diagnosis on CT requires 4 findings
Pleural abnormality: Pleural thickening, pleural effusion, or pleural plaque
Broad-based intimate attachment of mass-like consolidation to pleural abnormality
Volume loss
Comet tail (or hurricane) sign: Swirling of bronchovasculature into mass-like consolidation
Septic Emboli
Patients with indwelling catheters or IV drug users at risk
Multiple peripheral/subpleural nodules and wedge-shaped consolidation with rapid cavitation
Feeding vessel sign: Vessel leads directly to peripheral nodule or wedge-shaped consolidation
Exudative pleural effusion, often loculated
Pulmonary Contusions
Acute trauma clinical setting
Peripheral
Under point of blunt kinetic energy absorption
Often lateral portions of lung away from overlying musculature
Overlying rib fractures
Can occur without rib fractures in children and young adults
Appear at time of injury
Resolve in 3-5 days
Associated with other injuries but can be isolated
Associated with ballistic injuries
Helpful Clues for Less Common Diagnoses
Pulmonary Infarction
Most often from pulmonary arterial embolism
Often in setting of superimposed cardiac dysfunction (cardiomyopathy, congestive heart failure)
Both pulmonary and bronchial arterial supply to lung reduced
Lower lung predominant, peripheral/subpleural, wedge-shaped consolidation
Resolves over months (retains its original shape) rather than patchy resolution as in pneumonia
Cryptogenic Organizing Pneumonia
Bilateral, basal-predominant, peripheral and peribronchovascular consolidation
Scattered areas of ground-glass opacities and nodules
Atoll sign (a.k.a. reversed halo sign): Central ground-glass opacity surrounded by rim of consolidation
Perilobular opacities: Ill-defined opacities outlining interlobular septa of secondary pulmonary lobule
Chronic Eosinophilic Pneumonia
Peripheral, upper lung consolidation (so-called photographic negative of pulmonary edema)
Ground-glass opacities do not predominate
Waxing and waning disease course
Tendency to resolve centripetally (from outer to inner)
Residual band of linear opacities parallels chest wall late in evolution of disease
Usual Interstitial Pneumonitis
Peripheral and basal predominant distribution; costophrenic angles most affected
Volume loss
Reticular opacities, linear opacities, architectural distortion
Traction bronchiectasis and honeycombing
Ground-glass opacities do not predominate
Mild mediastinal lymphadenopathy not uncommon
Desquamative Interstitial Pneumonia
Slowly progressive dyspnea and cough in smoker
Basal and peripheral/subpleural ground-glass opacities; may be diffuse
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