Helen T. Winer-Muram, MD

Axial HRCT shows bilateral subpleural curvilinear opacities image in a patient with mild asbestosis. Subpleural lines persist on prone images (not shown).

Axial HRCT in the same patient shows peripheral ground-glass opacities image and septal lines image. Note the diaphragmatic plaques image.



  • Asbestosis: Interstitial lung disease due to inhalation of asbestos fibers


General Features

  • Best diagnostic clue: Basilar interstitial fibrosis and pleural plaques

  • Patient position/location: Posterobasilar subpleural lung

  • Morphology: Fibrosis centered on respiratory bronchioles

CT Findings

  • Morphology

    • Reticular (linear opacities) most common manifestation

      • Short intralobular or interlobular septal thickening

    • Centrilobular nodules or branching opacities earliest manifestation

      • Reflects fibrosis around small airways where fibers located

    • Subpleural curvilinear lines

      • Parallel chest wall within 1 cm of the pleura, length 5-10 cm

      • Represent peribronchial confluent fibrosis or atelectasis associated with obstructed respiratory bronchioles

      • Not specific for asbestosis

    • Parenchymal bands project perpendicular from pleura

      • 2-5 cm long

      • Fibrosis along interlobular septa or bronchovascular bundles

    • Small airways obstruction (from fibrosis incited by asbestos fibers)

      • May result in mosaic perfusion pattern

      • Traction bronchiolectasis is uncommon (more common in idiopathic pulmonary fibrosis)

    • Fibrosis with traction bronchiectasis and honeycombing in advanced disease

    • Pleural plaques (80%), best finding to differentiate from idiopathic pulmonary fibrosis

  • Distribution

    • Peripheral basilar lung most common distribution

      • Reflects initial location of deposited fibers

      • Because fibers are too large to be removed by macrophages, fibers tend to reflect initial deposition

Radiographic Findings

  • Radiography

    • May be normal (10-20%); pleural plaques (25%)

    • International Labor Office (ILO) classification compared to standard radiographs “B” reading

      • Asbestosis generally s, t, or u opacities

    • Late: End-stage honeycombing; progressive massive fibrosis extremely rare

    • Lung cancer: Lower zone predominance in contrast to upper zone predominance in general population of smokers

Imaging Recommendations

  • Best imaging tool

    • CT useful to differentiate lung nodules from pleural plaques, round atelectasis, and lung fibrosis

      • 10% of asbestos-exposed workers screened by CT for asbestosis will have lung mass

    • Screening asbestos-exposed workers

      • Of those with clinical asbestosis: Chest radiographs abnormal in 80%; HRCT abnormal in 96%

      • 33% with neither clinical nor chest radiographic evidence of asbestosis abnormal at HRCT

      • However, false-negatives for early asbestosis (25%)

  • Protocol advice: Prone scans help to differentiate true interstitial lung disease from gravity-related physiology


Idiopathic Pulmonary Fibrosis

  • No pleural plaques

  • Ground-glass opacities and traction bronchiolectasis are more common

  • Band-like opacities and mosaic pattern of perfusion are less common


  • No plaques; however, pleural thickening and pseudoplaques are common

  • Dilated esophagus

Rheumatoid Arthritis

  • No plaques; arthritis and joint erosions

Hypersensitivity Pneumonitis

  • No plaques

  • Less severe in costophrenic angles, more severe in mid and upper lungs

  • Mosaic perfusion from air-trapping, more common

Cytotoxic Drug Reaction

  • No plaques; interstitial thickening similar

  • Prototypical drug: Methotrexate

Lymphangitic Tumor

  • No plaques but pleural effusion and lymphadenopathy are common

  • Asymmetric distribution

  • Nodular thickening of septa and core bronchovascular structures


General Features

  • General path comments

    • Asbestos mineral properties: Heat resistant, high tensile strength, flexible, durable

      • 2 types of fibers: Serpentine and amphibole

    • Serpentine (chrysotile or white asbestos, 90% commercial asbestos)

      • Curly, wavy fiber, long (> 100 µm), diameter (20-40 µm)

    • Amphibole

      • Crocidolite (blue asbestos), amosite (brown asbestos), anthophyllite, tremolite, actinolite

      • Straight rigid fiber; length:width = 3:1 is aspect ratio

    • Retention: Long thin fibers > short thick fibers

    • Asbestos (ferruginous) bodies

      • Hemosiderin-coated fiber (mostly amphibole)

      • Incompletely phagocytized by macrophages

      • Not pathognomonic for asbestosis

      • Coated fibers fewer than uncoated fibers

      • Not correlated with fibrosis

    • Pathophysiology

      • Increased deposition of fibers in lower lung zones due to gravitational ventilatory gradient

      • Fibers deposit in respiratory bronchioles

      • No lymphatic removal, largest and most harmful asbestos fibers too large to be removed by macrophages

  • Epidemiology

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Sep 20, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on Asbestosis
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