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Toronto Notes 2019 Chest Imaging
Consolidation
• pathogenesis:fluid(water,blood),inflammatoryexudates,protein,ortumourinalveoli
• findings
■ air bronchograms: lucent branching bronchi visible through opacification
■ airspace nodules: fluffy, patchy, poorly defined margins with later tendency to coalesce, may take on
lobar or segmental distribution ■ silhouette sign
• differentialdiagnosis
■ fluid: pulmonary edema, blood (trauma, vasculitis, bleeding disorder, pulmonary infarct)
■ inflammatory exudates: bacterial infections, TB, allergic hypersensitivity alveolitis, COP
(Cryptogenic organizing pneumonia), allergic bronchopulmonary aspergillosis, aspiration,
sarcoidosis
■ protein: pulmonary alveolar proteinosis
■ tumour: bronchoalveolar carcinoma, lymphoma
• management:variesdependingonthepatternofconsolidation,whichcansuggestdifferentetiologies; should also be done in the context of clinical picture
Interstitial Disease
• pathogenesis:pathologicalprocessinvolvingtheinterlobularconnectivetissue(i.e.“scaffoldingofthe lung”)
• findings
■ septal thickening: fine lines caused by thickened connective tissue septae (most commonly due to
pulmonary edema or lymphangitis carcinomatosis).
■ these manifest on Chest Xray as:
◆ Kerley A: long thin lines in upper lobes
◆ Kerley B: short horizontal lines extending from lateral lung margin ◆ Kerley C: diffuse linear pattern throughout lung
■ nodular: 1-5 mm well-defined nodules distributed evenly throughout lung
◆ seen in malignancy, pneumoconiosis, and granulomatous disease (e.g. sarcoidosis, miliary TB)
■ reticular: fine curvilinear opacities
◆ seen in interstitial lung diseases (pulmonary fibrosis) ◆ watch for pneumothorax as a complication
■ reticulonodular: combination of reticular and nodular patterns
■ may also see signs of airspace disease (atelectasis, consolidation)
• differentialdiagnosis
■ occupational/environmentalexposure
◆ inorganic: asbestosis, coal miner’s pneumoconiosis, silicosis, berylliosis, talc pneumoconiosis
◆ organic: hypersensitivity pneumonitis, bird fancier’s lung, farmer’s lung (mouldy hay), and other
organic dust
■ autoimmune: Connective tissue diseases. (e.g. rheumatoid arthritis, scleroderma, SLE, polymyositis,
mixed connective tissue disease), IBD, celiac disease, vasculitis
■ drug-related: antibiotics (cephalosporins, nitrofurantoin), NSAIDs, phenytoin, carbamazepine,
fluoxetine, amiodarone, chemotherapy (e.g. methotrexate), heroin, cocaine, methadone
■ infections: non-tuberculous mycobacteria, certain fungal infections
■ idiopathic: hypersensitivity pneumonitis, IPF, BOOP
■ for Causes of Interstitial Lung Disease Classified by Distribution, see Respirology, R13
■ management: high-resolution CT thorax and biopsy
Pulmonary Nodule
• findings:roundopacity±silhouettesign
■ note: do not mistake nipple shadows for nodules; if in doubt, repeat CXR with nipple markers
• differentialdiagnosis
■ extrapulmonary density: nipple, skin lesion, electrode, pleural mass, bony lesion ■ solitary nodule
◆ tumour: carcinoma, hamartoma, metastasis, bronchial adenoma
◆ inflammation: histoplasmoma, tuberculoma, coccidioidomycosis
◆ vascular: AV fistula, pulmonary varix (dilated pulmonary vein), infarct, embolism
■ multiple nodules: metastases, abscess, granulomatous lung disease (TB, fungal, sarcoid, rheumatoid nodules, silicosis, GPA)
• management:clinicalinformationandCTappearancedeterminelevelofsuspicionofmalignancy ■ if high probability of malignancy, invasive testing (fine needle aspiration, transbronchial/
transthoracic biopsy) is indicated
■ if low probability of malignancy, follow up imaging as per Fleishner guidelines 2017
Medical Imaging MI7
Figure 7. Consolidation: bacterial pneumonia
Figure 8. Interstitial disease: fine reticular pattern
Figure9.Interstitialdisease:medium reticular pattern
DDx of Interstitial Lung Disease
FASSTEN (upper lung disease)
Farmer’s lung (hypersensitivity pneumonitis) Ankylosing spondylitis
Sarcoidosis
Silicosis
TB
Eosinophilic granuloma (Langerhans cell histiocytosis)
Neurofibromatosis
BAD RASH (lower lung disease)
BOOP
Asbestos
Drugs (nitrofurantoin, hydralazine, isoniazid, amiodarone, many chemotherapy drugs) Rheumatological disease
Aspiration
Scleroderma
Hamman Rich (IPF) and idiopathic pulmonary fibrosis
DDx for Cavitating Lung Nodule
WEIRD HOLES
GPA (Wegener’s)
Embolic (pulmonary, septic)
Infection (anaerobes, pneumocystis, TB) Rheumatoid (necrobiotic nodules) Developmental cysts (sequestration) Histiocytosis
Oncological Lymphangioleiomyomatosis Environmental, occupational Sarcoidosis