CONTENTS
abbreviations used in the pulmonary section:
- AE-ILD: Acute exacerbation of ILD 📖
- AIP: Acute interstitial pneumonia (Hamman-Rich syndrome) 📖
- ANA: Antinuclear antibody 📖
- ANCA: Antineutrophil cytoplasmic antibodies 📖
- ARDS: Acute respiratory distress syndrome 📖
- ASS: Antisynthetase Syndrome 📖
- BAL: Bronchoalveolar lavage 📖
- BiPAP: Bilevel positive airway pressure 📖
- COP: Cryptogenic organizing pneumonia 📖
- CPAP: Continuous positive airway pressure 📖
- CPFE: Combined pulmonary fibrosis and emphysema 📖
- CTD-ILD: Connective tissue disease associated interstitial lung disease 📖
- CTEPH: Chronic thromboembolic pulmonary hypertension 📖
- DAD: Diffuse alveolar damage 📖
- DAH: Diffuse alveolar hemorrhage 📖
- DIP: Desquamative interstitial pneumonia 📖
- DLCO: Diffusing capacity for carbon monoxide 📖
- FEV1: Forced expiratory volume in 1 second 📖
- FVC: Forced vital capacity 📖
- GGO: Ground glass opacity 📖
- GLILD: Granulomatous and lymphocytic interstitial lung disease 📖
- HFNC: High flow nasal cannula 📖
- HP: Hypersensitivity pneumonitis 📖
- IPAF: Interstitial pneumonia with autoimmune features 📖
- IPF: Idiopathic pulmonary fibrosis 📖
- IVIG: Intravenous immunoglobulin 📖
- LIP: Lymphocytic interstitial pneumonia 📖
- MCTD: Mixed connective tissue disease 📖
- NIV: Noninvasive ventilation (including CPAP or BiPAP) 📖
- NSIP: Nonspecific interstitial pneumonia 📖
- NTM: Non-tuberculous mycobacteria 📖
- OP: Organizing pneumonia 📖
- PAP: Pulmonary alveolar proteinosis 📖
- PE: Pulmonary embolism 📖
- PFT: Pulmonary function test 📖
- PPFE: Pleuroparenchymal fibroelastosis 📖
- PPF: Progressive pulmonary fibrosis 📖
- PVOD/PCH Pulmonary venoocclusive disease/pulmonary capillary hemangiomatosis 📖
- RB-ILD: Respiratory bronchiolitis-associated interstitial lung disease 📖
- TNF: tumor necrosis factor
- UIP: Usual Interstitial Pneumonia 📖
- A cavity is defined as a gas-filled space within a nodule, mass, or area of parenchymal consolidation.
- Cavitation is important for a few reasons:
- (1) Cavitation usually implies a necrotic process, with destruction of lung tissue. Such processes may pose a risk of ongoing and permanent lung damage.
- (2) Cavitation is often associated with important, treatable lung diseases (e.g., tuberculosis, malignancy).
- The differentiation between cavitation versus other cavity-like disorders (such as cysts, blebs, and bullae) is discussed further here: 📖
infection
malignancy
- Lung cancer (~75% squamous cell carcinoma; less often adenocarcinoma or large cell carcinoma).(25623513)
- Metastasis:
- Metastatic squamous cell carcinoma (especially from head/neck, esophagus, or cervix primary).
- Metastatic adenocarcinoma (e.g., choriocarcinoma).
- Melanoma.
- Sarcoma (often cavitates, yet is infrequent).
- Gastrointestinal malignancy rarely causes multiple tiny cavitary nodules (“Cheerio sign”).(29518379)
- Pulmonary lymphoma.
- Lymphomatoid granulomatosis.
inflammatory
- GPA (granulomatosis with polyangiitis). 📖
- Rheumatoid arthritis necrobiotic nodules. 📖
- Extremely rare:
- Sarcoidosis (primary cavitary sarcoidosis). This is rare, so the possibility of coexisting mycobacterial infection should be considered. (25623513)
- Pulmonary pyoderma gangrenosum.
other
- Pulmonary infarction (due to pulmonary embolism). Cavitation is more likely with septic emboli, but it can also occur with bland emboli.
location
- Apex: suggests mycobacteria, fungus, or squamous cell carcinoma.
- Anterior upper lobe: suggests malignancy.
- Lung abscess: tends to occur in the posterior segments of the upper lobes or superior segments of the lower lobes.(32934178)
- Multifocal, peripheral cavitation: suggests septic emboli.
number of cavitary lesions
solitary cavitary lesion may suggest:
- Primary lung cancer.
- Infection:
- Lung abscess.
- Fungal infection.
- Tuberculosis.
multiple cavitary lesions may suggest:
- Metastatic cancer or lymphoma.
- Infection:
- Tuberculosis.
- Invasive aspergillosis.
- Coccidiomycosis.
- Septic pulmonary emboli.
- GPA (granulomatosis with polyangiitis).
- Rheumatoid nodules.(32934178)
thick wall & irregularity
- Malignancy:
- >15 mm is suggestive of malignancy (usually squamous cell carcinoma). However, ~15% of lung abscesses may have a wall thickness >15 mm.(Rosado-de-Christenson 2022)
- Malignancy may produce a nodular cavity wall. (29518379) If there is an enhancing mural nodule, this may be especially worrisome for malignancy. (25623513)
- Lung abscess: usually has a smooth (90%) or shaggy (10%) wall.(Rosado-de-Christenson 2022)
tree-in-bud opacities
- Tree-in-bud opacities suggest an infectious process, especially mycobacteria (either tuberculosis or non-tuberculous mycobacteria).
- Other possibilities:
- Aspiration.
- CCPA (chronic cavitary pulmonary aspergillosis).
- (Additional discussion of tree-in-bud opacities: 📖).
cavitation with surrounding ground glass opacities (halo sign)
- Septic pulmonary emboli.
- Fungal infection:
- Invasive mold infection (e.g., aspergillosis, mucormycosis).
- Coccidiomycosis.
- Mycobacteria (tuberculous or non-tuberculous).
- Certain malignancies, including:
- Melanoma.
- Sarcomas.
- Choriocarcinoma.
- GPA (granulomatosis with polyangiitis).
- (Further discussion of the halo sign: 📖).
air-crescent sign (aka, meniscus sign)
basics:
- The air-crescent sign is defined as a crescent of air surrounding a pulmonary parenchymal nodule or mass.(30707061)
- This may occur in two ways:
- (1) Necrosis of a patch of lung tissue, which subsequently contracts.
- (2) Accumulation of debris or blood within a pre-existing cavity.
causes of the air-crescent sign:
- Infection:
- Mold:
- Invasive pulmonary aspergillosis (typically occurring during a recovery phase, when neutrophil counts are rising).
- Aspergilloma is the most common cause (fungal ball developing within a pre-existing cavity). Fungal ball may be mobile, depending on the patient's position.
- Necrotizing bacterial pneumonia (with internal necrotic debris).
- Echinococcal cyst.
- Mold:
- Cavitating neoplasm (primary > metastatic).
- Intracavitary blood clot (e.g., due to pulmonary infarction, traumatic pneumatocele).
- Pseudoaneurysm along the wall of a cavity (called a Rasmussen aneurysm within the context of a tuberculous cavity).
- Granulomatosis with polyangiitis.
investigation may include:
- Prone images: Mobility of the mass within the cavity may suggest aspergilloma or intracavitary blood clot.
- Contrast administration:
- Strong enhancement may reveal the presence of a pseudoaneurysm within the cavity wall. Although uncommon, a pseudoaneurysm is critical to establish because it completely changes the diagnostic and therapeutic approach (biopsy is contraindicated; angiography for embolization may be life-saving).
- Weak enhancement may be seen with malignancies.
Cheerios sign (aka open bronchus sign)
definition
- Radiologically defined as pulmonary nodules with central lucency resembling Cheerios.
- Causes:
- May result from a proliferation of neoplastic or non-neoplastic cells around a patent airway.
- May represent small cavitary lesions.
causes
- Malignancy (usually lepidic-predominant adenocarcinoma).
- Primary lung cancer.
- Metastatic carcinoma.
- Lymphoma.
- Fungal infections.
- Rheumatoid nodules.
- GPA (granulomatosis with polyangiitis).
- PLCH (pulmonary Langerhans cell histiocytosis).(28212835)
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References
- 25623513 Mortensen KH, Babar JL, Balan A. Multidetector CT of pulmonary cavitation: filling in the holes. Clin Radiol. 2015 Apr;70(4):446-56. doi: 10.1016/j.crad.2014.12.010 [PubMed]
- 28212835 Raju S, Ghosh S, Mehta AC. Chest CT Signs in Pulmonary Disease: A Pictorial Review. Chest. 2017 Jun;151(6):1356-1374. doi: 10.1016/j.chest.2016.12.033 [PubMed]
- 29143119 Sevilha JB, Rodrigues RS, Barreto MM, Zanetti G, Hochhegger B, Marchiori E. Infectious and Non-Infectious Diseases Causing the Air Crescent Sign: A State-of-the-Art Review. Lung. 2018 Feb;196(1):1-10. doi: 10.1007/s00408-017-0069-3 [PubMed]
- 29518379 Gafoor K, Patel S, Girvin F, Gupta N, Naidich D, Machnicki S, Brown KK, Mehta A, Husta B, Ryu JH, Sarosi GA, Franquet T, Verschakelen J, Johkoh T, Travis W, Raoof S. Cavitary Lung Diseases: A Clinical-Radiologic Algorithmic Approach. Chest. 2018 Jun;153(6):1443-1465. doi: 10.1016/j.chest.2018.02.026 [PubMed]
- 30707061 Fan K, Lee C. Imaging Evolution of an Invasive Fungal Infection in a Neutropenic Patient. Ann Am Thorac Soc. 2019 Feb;16(2):271-274. doi: 10.1513/AnnalsATS.201808-566CC [PubMed]
- 31704148 Gruden JF, Naidich DP, Machnicki SC, Cohen SL, Girvin F, Raoof S. An Algorithmic Approach to the Interpretation of Diffuse Lung Disease on Chest CT Imaging: A Theory of Almost Everything. Chest. 2020 Mar;157(3):612-635. doi: 10.1016/j.chest.2019.10.017 [PubMed]
- 32934178 Canan A, Batra K, Saboo SS, Landay M, Kandathil A. Radiological approach to cavitary lung lesions. Postgrad Med J. 2021 Aug;97(1150):521-531. doi: 10.1136/postgradmedj-2020-138694 [PubMed]
- 35680314 Shayani KE, Birnbaum B, Machnicki S, Hajiyeva S, Lazzaro R, Mina B. Cough and Progressive Pleuritic Chest Pain With an Enlarging Cavity on Imaging. Chest. 2022 Jun;161(6):e349-e354. doi: 10.1016/j.chest.2022.01.030 [PubMed]
Books:
- Shah, P. L., Herth, F. J., Lee, G., & Criner, G. J. (2018). Essentials of Clinical pulmonology. In CRC Press eBooks. https://doi.org/10.1201/9781315113807
- Shepard, JO. (2019). Thoracic Imaging The Requisites (Requisites in Radiology) (3rd ed.). Elsevier.
- Walker C & Chung JH (2019). Muller’s Imaging of the Chest: Expert Radiology Series. Elsevier.
- Palange, P., & Rohde, G. (2019). ERS Handbook of Respiratory Medicine. European Respiratory Society.
- Rosado-De-Christenson, M. L., Facr, M. L. R. M., & Martínez-Jiménez, S. (2021). Diagnostic imaging: chest. Elsevier.
- Murray & Nadel: Broaddus, V. C., Ernst, J. D., MD, King, T. E., Jr, Lazarus, S. C., Sarmiento, K. F., Schnapp, L. M., Stapleton, R. D., & Gotway, M. B. (2021). Murray & Nadel’s Textbook of Respiratory Medicine, 2-Volume set. Elsevier.
- Fishman's: Grippi, M., Antin-Ozerkis, D. E., Cruz, C. D. S., Kotloff, R., Kotton, C. N., & Pack, A. (2023). Fishman’s Pulmonary Diseases and Disorders, Sixth Edition (6th ed.). McGraw Hill / Medical.
