Key points
Background
Main text
COVID-19 pneumonia
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subpleural, bilateral or less frequently unilateral, opacities, which are commonly located in the inferior lobes;
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possible evidence of peripheral pulmonary vessel widening;
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rarity of pleural effusions, pulmonary nodules and mediastinal lymphadenopathies.
Stage | Phase | Timing (days) | Predominant radiological findings | Additional findings | Spatial distribution of radiological findings |
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1 | Early | 0–4 | Ground-glass opacities | Peripheral vessel widening Halo sign Atoll sign or reversed halo sign Overlapping of radiological findings in different phases Rarity of: lymphadenopathies, pleuric effusions, pulmonary nodules | Bilateral Peripheral/subpleural Centroparenchymal (atypical) Lower lobes prevalence |
2 | Progressive | 5–8 | Crazy paving pattern, ground-glass opacities and small consolidations | ||
3 | Peak | 9–13 | Consolidative foci | ||
4 | Absorption | ≥ 14 | Ground-glass opacities and linear consolidation |
Differential diagnoses
Pathologies | Ground glass | Crazy paving | Consolidations | |
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Infective pneumonia | Bacterial | R (ATYPICAL) | OD/A | C (TYPICAL) |
Viral | C | OD/A | R | |
Fungal: pneumocystis jiroveci pneumonia | C | R | R | |
Fungal: angioinvasive aspergillosis | (HALO) | OD/A | C | |
Cardiovascular | Acute pulmonary oedema | C (INTERSTITIAL) | C (INTERSTITIAL) | C (ALVEOLAR) |
Acute pulmonary embolism and infarctions | C | C | C | |
Vasculitis | C (HAEMORRAGE) | C (REABSORPTION) | C (MASSIVE HAEMORRAGE) | |
Hypersensitivity pneumonia | C | OD/A | R | |
Eosinophilic pneumonia | Simple pulmonary eosinophilia | C | OD/A | C |
Acute eosinophilic pneumonia | C | C | R | |
Chronic eosinophilic pneumonia | R | R | C | |
Aspiration pneumonia | Fluid-related ab ingestis pneumonia | C | OD/A | C |
Chronic lipoid pneumonia | C | C | C | |
Alveolar proteinosis | OD/A | C | R |
Infective pneumonia
Bacterial pneumonia
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additional findings as centrilobular nodules, cavitations and pneumatoceles (more common in S. aureus pneumonia) [22];
Viral pneumonia
Pneumocystis jiroveci pneumonia
Angioinvasive aspergillosis
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in case of consolidations with no ground-glass halo and absence of other ground-glass opacities, COVID-19 pneumonia is unlikely;
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lymphadenomegalies and pleural effusions [29].
Cardiovascular pathologies
Pulmonary oedema
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possible coexistence of ground-glass opacities, crazy paving pattern and consolidations with different timing of occurrence respect to COVID-19 pneumonia, crazy paving being the first pattern to be appreciated in interstitial oedema;
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diffuse, bilateral, centro-parenchymal crazy paving and ground-glass opacities with subpleural preservation. Consolidations are late findings and generally coexist with pleural effusions;
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bilateral pleural effusions, more evident in the alveolar phase of oedema;
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mediastinal lymphadenomegalies;
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cardiomegaly.
Acute pulmonary embolism (APE)
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different phases of infarction maturation, in correlation to the onset time;
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segmental shape of infarctions are located in the vascular territories of the occluded vessels;
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presence of vessel embolus, vessel occlusion and residual peripheral clot deposition.
Vasculitis
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coexistence of bronchial and tracheal thickening in granulomatosis with polyangiitis;
Hypersensitivity pneumonia
Eosinophilic pneumonia
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migrant lesions with absence of crazy paving pattern in SPE (simple pulmonary eosinophilia, also known as Loeffler syndrome) [46];
Aspiration pneumonia
Fluid aspiration pneumonia
Lipoid pneumonia
Pulmonary alveolar proteinosis (PAP)
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mainly centro-parenchymal and perihilar crazy paving areas [61];
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juxtaposition of severely affected secondary lobules and normal secondary lobules;
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rarely, consolidations with air bronchogram in severe forms [61];
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fibrotic alterations in advanced stage;
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pleural effusions, cardiomegaly and lymphadenomegalies, which are features of complicated PAP.