Definition
- Presence of hazy increased opacities of the lung, with preservation of bronchial and vascular margins.
- Focal or diffuse.
- Non-specific finding on CT and may represent various pathology (e.g., alveolar wall inflammation/thickening, partial airspace filling, a reduction of air in the alveolar airspaces, etc.).
Acute Etiologies
- Low lung volumes or normal expiration.
- Pulmonary edema.
- Aspiration.
- Diffuse alveolar damage (e.g., pathologic correlate of ARDS).
- Hemorrhage.
- Infection.
- Opportunistic: PCP, CMV, HSV.
- Non-opportunistic: atypical pneumonia (e.g. mycoplasma), Covid-19, MERS, SARS.
- Early ILD: acute interstitial pneumonia, acute eosinophilic pneumonia, hypersensitivity pneumonitis.
- Drug toxicities.
Chronic Etiologies
- Eosinophilic pneumonia.
- Hypersensitivity pneumonitis.
- Interstitial lung diseases.
- Often correlates with fibrosis with evidence of traction bronchiectasis.
- Pulmonary alveolar proteinosis.
- Organizing pneumonia.
- Sarcoidosis.
- Neoplastic processes.
- Adenocarcinoma in situ (formerly bronchoalveolar carcinoma).
Collins J, Stern EJ. Ground-glass opacity at CT: the ABCs. AJR Am J Roentgenol 1997;169:355-367.
El-Sherief AH et al. Clear Vision through the Haze: A practical Approach to Ground Glass Opacity. Current Problems in Diagnostic Radiology 2014; 43(3) 140-158.