Cryptogenic Organizing Pneumonia

Cryptogenic Organizing Pneumonia

Jud W. Gurney, MD, FACR

Axial HRCT shows peribronchial consolidation, ground-glass opacities image, and irregular subpleural mass-like consolidation image.

Axial HRCT show a large area of consolidation image and smaller peribronchial consolidation image from cryptogenic organizing pneumonia.


Abbreviations and Synonyms

  • Cryptogenic organizing pneumonia (COP), secondary organizing pneumonia (SOP), proliferative bronchiolitis, idiopathic bronchiolitis obliterans organizing pneumonia (BOOP)


  • Clinicopathological entity characterized by polypoid plugs of loose granulation tissue within air spaces


General Features

  • Best diagnostic clue: Bilateral, peripheral, basal, nodular consolidation

  • Patient position/location: Typically in mid and lower zones

  • Size: Tiny nodules to whole lobes

CT Findings

  • Multiple patterns

    • Multiple alveolar opacities (90%)

      • Size of consolidation from few cm in size to whole lobe

      • Often admixed with ground-glass opacities

      • Air-bronchograms common, often dilated

      • Bilateral, lower zones

      • Lung volumes preserved

      • Axial plane: Subpleural or bronchovascular (75%)

      • May be migratory and wax and wane over weeks to months

      • More common in immunocompetent compared to immunocompromised patients

      • Presence of consolidation associated with greater likelihood of partial or complete response to treatment

    • Multiple pulmonary nodules (10%)

      • < 5 mm diameter (40%), > 5 mm diameter (60%)

      • May have air-bronchograms

      • No zonal predominance

  • Solitary alveolar opacity (10%)

    • Mimics bronchogenic carcinoma

    • < 3 cm (60%) or > 3 cm diameter (40%)

      • Median diameter 1.9 cm

    • More common upper lung zones (60%) vs. lower lung zones (40%)

    • Subpleural (40%), peripheral bronchovascular (33%), or peripheral (30%)

    • Round (30%); flat, oval, or trapezoidal (70%)

    • Pleural tag (50%)

    • Irregular margin (spiculated) (95%)

    • Satellite nodules (55%)

    • Vessels converge at edge of lesion (80%)

    • May be cavitary

  • Reticular interstitial pattern (< 10%)

    • Overlaps with idiopathic pulmonary fibrosis or nonspecific interstitial pneumonia

    • Signifies fibrosis

  • Associated findings in patients with multiple alveolar opacities

    • Band-like opacities, 2 patterns

      • Linear opacities paralleling bronchial course toward pleura

      • Subpleural lines, unrelated to bronchi

    • Pleural effusions less common (10%), when present small

    • Mediastinal adenopathy (20%)

  • Perilobular pattern

    • Consolidation outlines periphery of secondary pulmonary lobule

    • May form arcades and polygonal opacities that extend to pleural surface like fish scales or tiles on a roof (imbricate)

    • Perilobular consolidation not as sharply defined as thickened interlobular septa in pulmonary edema

    • More predominant in mid and lower lung zones

    • Seen in 50% but not specific for COP

  • Reverse halo sign

    • Central ground-glass opacity surrounded by denser crescentic (semicircular to circular) consolidation at least 2 mm in thickness

    • Also known as atoll sign

    • Seen in 20% but not specific for COP

      • Also described in lymphomatoid granulomatosis and paracoccidioidomycosis

Radiographic Findings

  • Radiography

    • Findings less well identified compared to CT

    • Focal or multifocal consolidation, remains chronic after course of antibiotic therapy; clue to conditions that give chronic consolidation pattern

      • Chronic consolidation arbitrarily defined as persistent more than 30 days

    • Differential for chronic consolidation

      • Bronchioloalveolar cell carcinoma

      • Cryptogenic organizing pneumonia

      • Alveolar sarcoidosis

      • Alveolar proteinosis

      • Lymphoma or pseudolymphoma

      • Chronic eosinophilic pneumonia

      • Lipoid pneumonia

      • Chronic aspiration


Chronic Eosinophilic Pneumonia

  • Usually in upper lung zone (eosinophilia absent in COP)

  • Nodules, nonseptal linear pattern, reticulation and peri-bronchiolar distribution more common in COP

  • Septal lines more common in chronic eosinophilic pneumonia

Bronchioloalveolar Cell Carcinoma (BAC)

  • BAC not predominately subpleural

  • Foci usually predominantly ground-glass opacities

Sarcoidosis, Alveolar

  • Few large airspace masses with air-bronchograms

  • Preferentially involves upper lung zones

  • Usually associated with symmetric hilar and mediastinal adenopathy

Lung Cancer (Solitary Mass)

  • Organizing pneumonia more commonly has

    • Broad contact with pleura or centered on bronchi

    • Flat, oval, or trapezoidal shape

    • Satellite lesions


  • Opacities not as chronic or peripheral as COP

  • Predominately in dependent lung segments

  • Typical predisposing conditions: Esophageal motility disorder, obtundation, alcoholism

Lipoid Pneumonia

  • Lipoid pneumonia may have fat density in areas of consolidated lung at CT

  • May present with “crazy-paving” appearance on CT

  • History of lipoid ingestion: Oily nose drops, mineral oil

Sep 20, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on Cryptogenic Organizing Pneumonia

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