Citation, DOI, disclosures and article data
Citation:
Gaillard F, Silverstone L, Bickle I, et al. Air crescent (lung). Reference article, Radiopaedia.org (Accessed on 06 Oct 2024) https://doi.org/10.53347/rID-869
Air crescent describes the crescent of gas between an intra-cavitary mass and the cavity wall. The intra-cavitary mass may be due to necrotic tissue or a fungus ball 6.
Terminology
The descriptor Monod sign 2 is commonly used to describe the combination of a gas crescent and a mobile fungus ball. The 2024 Fleischner glossary no longer includes this term and uses ‘air crescent’ to refer to gas in cavities that contain mobile fungal balls as well as those that contain fixed infarcted tissue 8.
Pathology
Etiology
Common causes include angio-invasive aspergillosis with retraction of infarcted lung, fungal colonization of a preexisting cavity or blood clot 8. Fungal balls can be mobile.
Causes include 5:
In angioinvasive fungal infection, the nodules are composed of infected hemorrhagic and infarcted lung tissue. As the neutrophil count recovers and the patient mounts an immune response, peripheral reabsorption of necrotic tissue causes the retraction of the infarcted center and air fills the space in between 7. This creates an air crescent within the nodules and is a good prognostic finding because it marks the recovery phase of the infection. This sign is seen in ~50% of patients 2.
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1. Abramson S. The air crescent sign. Radiology. 2001; 218(1): 230-2. Radiology [pubmed citation]
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2. Thompson BH, Stanford W, Galvin JR, et al. Varied radiologic appearances of pulmonary aspergillosis. Radiographics. 1995; 15(6): 1273-84. Radiographics [pubmed citation]
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3. Müller Nestor L, Tomás Franquet, Kyung Soo Lee et al. Imaging of Pulmonary Infections: A Fundamental and Clinical Text. Third Edition. Lippincott Williams & Wilkins, 2006. ISBN: 078177232X.
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4. Yella LK, Krishnan P, Gillego V. The air crescent sign: A clue to the etiology of chronic necrotizing pneumonia. Chest. 2005; 127(1): 395-7. doi:10.1378/chest.127.1.395 [pubmed citation]
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5. Franquet Tomás, Nestor L. Müller, Ana Giménez et al. “Spectrum of Pulmonary Aspergillosis: Histologic, Clinical, and Radiologic Findings1.” Radiographics 21, no. 4 (July 2001): 825-837. Radiographics [pubmed citation]
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6. Enrique Cubillo-Herguera, William H. McAlister. The Pulmonary Meniscus Sign in a Case of Bronchogenic Carcinoma. (1969) Radiology. 92 (6): 1299-300. doi:10.1148/92.6.1299 - Pubmed
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7. Chiarenza A, Esposto Ultimo L, Falsaperla D, et al. Chest imaging using signs, symbols, and naturalistic images: a practical guide for radiologists and non-radiologists. (2019) Insights into imaging. 10 (1): 114. doi:10.1186/s13244-019-0789-4 - Pubmed
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8. Bankier A, MacMahon H, Colby T et al. Fleischner Society: Glossary of Terms for Thoracic Imaging. Radiology. 2024;310(2):e232558. doi:10.1148/radiol.232558 - Pubmed
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