Ground-Glass Opacity

Also known as GGO or subsolid nodule

By Luke Byers, MD and Rich Strongwater, MD

Reviewed by Charles L. Fishman, MD, FACP, FCCP

Chest X-rays demonstrating ground glass opacities due to pneumocystis jirovecii pneumonia. These chest radiographs are of two patients. Both show ground-glass opacities. The left chest X-ray (CXR) shows more subtle ground-glass opacities while the right CXR shows a much more pronounced ground-glass pattern mimicking pulmonary edema.

Generally, ground-glass opacity refers to areas of ill-defined attenuation within the lung parenchyma. When used on chest radiographs, the definition is less specific and generally refers to areas of hazy opacification (or hazy gray) with or without loss of bronchial or pulmonary artery definition. On chest computed tomography (CT) especially on High- Resolution CT, this opacity does not obscure pulmonary vessels or bronchial borders. If the vessels/bronchial borders are obscured by part/all of the opacity, it is termed a consolidation.

Signs and Symptoms related to Ground-Glass Opacity

The patient's signs or symptoms of ground-glass opacity are related to the underlying disease process. Many of these processes are more acute, and the patient may present with acute respiratory insufficiency.

Causes and Risk Factors

Ground-glass opacity may be caused by any process that may result in partial filling of the alveolar airspace or partial collapse of the airspace. Broadly, categories include:

• Infectious etiologies, including viral or opportunistic infections.

• Acute alveolar processes, including pulmonary edema, acute respiratory distress syndrome, or pulmonary hemorrhage.

• Multiple subcategories of interstitial lung disease, including nonspecific interstitial pneumonia, acute interstitial pneumonia, hypersensitivity pneumonitis, eosinophilic pneumonia, and smoking-related interstitial lung disease such as respiratory bronchiolitis-associated interstitial lung disease or desquamative interstitial pneumonia. This may also be seen with sarcoidosis.

• Primary pulmonary neoplasm (usually of a smaller size and lower grade).

• Drug toxicity.

• Pulmonary manifestations of vasculitides.

Key Recommendations

In the presence of clinical symptoms, ground-glass opacities can be associated with a  clinical infectious or inflammatory etiology. In patients with incidentally identified focal ground-glass nodule(s) (which would only be seen by CT), primary lung neoplasm should be considered and can be evaluated with follow-up or serial CT images. Follow-up is often guided by the Fleischner Society guidelines (most recent revision 2017). Recommendations are based on the size cut-off (6 mm) and presence of single or multiple ground-glass opacities. Patient's specific high-risk factors include history of smoking, exposure to carcinogens, emphysema, fibrosis, family history of lung cancer, advanced age, and male gender.

Fleischner Criteria

For a single ground-glass nodule < 6 mm, no routine follow-up is indicated unless there are suspicious features or growth.

For a single ground-glass nodule ≥ 6 mm, CT at 6-12 months and, if persistent, at 3 and 5 years are indicated. (More recently, the 2023 AATS consensus statement recommends the first follow-up CT scan at 6 months)

For a single mixed solid and ground-glass nodule < 6 mm, no routine follow-up is indicated, although assessing for a mixed component of the nodule this size is extremely difficult.

For single mixed solid and ground-glass nodule ≥ 6 mm, CT at 3-6 months and, if persistent and solid component remains < 6 mm, annual CT for 5 years are indicated. Solid component measurement > 6 mm should be considered highly suspicious for neoplasm.

For multiple ground-glass nodules < 6 mm, CT at 3-6 months is indicated and, if patient is stable, consider CT at 2 and 4 years. Typically, this would be a benign pattern, but more careful surveillance is suggested in high-risk patients. (the 2023 AATS consensus statement recommends first repeat CT scan in 3 months).

For multiple ground-glass nodules ≥ 6 mm, CT at 3-6 months with subsequent management guidelines by the most suspicious nodule(s) are indicated.

Pearl to Know

Ground-glass opacities or nodules are nonspecific. The patient's symptoms and history may help to reveal the underlying etiology.

Ground glass nodules, when caused by a benign or inflammatory process often resolve within 3 months.  A ground glass nodule that persists for more than 3 months may indicate a less benign etiology. 

If a persistent GGO develops a solid component, more aggressive workup would be indicated, and invasive adenocarcinoma should be considered.

Editor's comment- any subsequent follow up should be modified if high-risk patient.

Reference

Gordon N, Munshi R, Leef M, Joob A, Alraiyes A.  Cleveland Clinic Journal of Medicine. August 2026, 93 (8) 475-484; DOI: https://doi.org/10.3949/ccjm.93a.26004

Chen H, Kim A, Hsin M,  Tailor T,  Jones D,  Yanagawa J,  et al.  The 2023 American Association for Thoracic Surgery (AATS) Expert Consensus Document: Management of subsolid lung nodules. JTCVS  Volume 168, Issue 3p. 631-647,.e11. September 2024.