Ground-glass opacification

Last revised by Dr Daniel J Bell on 30 Oct 2021

Ground-glass opacification/opacity (GGO) is a descriptive term referring to an area of increased attenuation in the lung on computed tomography (CT) with preserved bronchial and vascular markings. It is a non-specific sign with a wide etiology including infection, chronic interstitial disease and acute alveolar disease.

Ground glass opacification is also used in chest radiography to refer to a region of hazy lung radiopacity, often fairly diffuse, in which the edges of the pulmonary vessels may be difficult to appreciate 7.

The use of the term ground glass derives from the industrial technique in glassmaking whereby the surface of normal glass is roughened by grinding it. 

Ground-glass opacities have a broad etiology:

  • normal expiration
    • on expiratory acquisitions, which can be detected if the posterior membranous wall of the trachea is flattened or bowed inwards
  • partial filling of air spaces
  • partial collapse of alveoli
  • interstitial thickening
  • inflammation
  • edema
  • fibrosis
  • lepidic proliferation of neoplasm

Broadly speaking, the differential for ground-glass opacification can be split into 5:

  • infectious processes (opportunistic vs non-opportunistic)
  • chronic interstitial diseases
  • acute alveolar diseases
  • other causes

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Cases and figures

  • Figure 1: ground glass stoppers (photo)
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  • Case 1: amiodarone lung
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  • Case 2: angioinvasive aspergillosis
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  • Case 3: sarcoidosis
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  • Case 4: COP
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  • Case 5: early COVID-19
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  • Case 6: H1N1 pneumonia
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