Learning objectives
To learn a step-by-step approach for narrowing the differential diagnosis of diffuse ground glass opacification (GGO).
To identify differentiating clinical and radiologic features that point to the most probable differential diagnosis.
Background
Diffuse GGO is a commonly encountered pattern in CT scans of the lung and can prove to be a very time-consuming finding,
as there are many possible differential diagnoses (1).
Following a step-by-step approach can help to narrow down the differentials,
as we will show in this exhibit.
Findings and procedure details
Pathophysiology of GGO on CT scans
Ground glass opacifications are one of the most commonly encountered pulmonary patterns in chest CTs.
The underlying mechanism is an increase in density caused by a partial filling or collapse of the alveoli or the thickening of the interstitial tissue (Fig.
1).
Alveoli may fill with:
Transudate (pulmonary edema,
inflammatory reaction)
Aspirated material
Hyaline (ARDS)
Mucins (mucinous adenocarcinoma of the lung,
pulmonary alveolar proteinosis)
Pus
Blood
Cells (adenocarcinoma,
lymphoma)
A collapse of alveoli may be triggered by:
Longstanding obstruction...
Conclusion
Three questions guide the differential diagnosis of diffuse GGO:
Is it a pathology?
Is the GGO acute or chronic?
What is the patient's medical history?
Followed by the review of imaging findings regarding:
Spatial and temporal distribution of GGO
Ancillary imaging findings
References
(1) Collins J,
Stern EJ.
Ground-glass opacity at CT: the ABCs.
AJR American journal of roentgenology.
1997;169(2):355-67.
(2) Müller NL,
Franquet T,
Lee KS et-al.
Imaging of pulmonary infections.
Lippincott Williams & Wilkins.
(2007) ISBN:078177232X.
(3) Collins,
Jannette,
and Eric J.
Stern.
2012.
Chest Radiology: The Essentials.
Lippincott Williams & Wilkins.
(4) Elicker,
Brett M.,
and W.
Richard Webb.
2012.
Fundamentals of High-Resolution Lung CT: Common Findings,
Common Patters,
Common Diseases and Differential Diagnosis.
Lippincott Williams & Wilkins.