A categorical approach to thoracic imaging

A Categorical Approach to Thoracic Imaging Marc V. Gosselin, MD his hand out summarizes most of the information in the issue. It is by no means a complete list of diseases but does contain the more commonly encountered disorders. The goal is to build upon the radiologist's current conceptual framework when he or she approaches common imaging manifestations of pulmonary diseases. These diseases are organized according to either their predominate morphological imaging characteristic or their anatomic distribution. Both the imaging appearance and distribution need to be evaluated on each thoracic imaging examination. The ancillary findings should help the radiologist to narrow the differential possibilities and to render a short differential or the diagnosis in many instances. It is hoped this outline will at least give a practical starting point for the radiologist and clinician when confronted with a diffuse lung disease pattern on imaging studies. However, it is important to remember that if the clinical and radiographic findings do not correlate, then further evaluation with follow-up studies or tissue sampling is often necessary. This helps to ensure that unusual etiologies or atypical presentations of common diseases are not missed. Pulmonary medicine and lung pathology are experiencing a rapid evolution in the understanding of numerous diffuse lung diseases. Consequently, the imaging manifestations of these diseases are concurrently evolving. As a result, the categorical approach listed here has also evolved frequently over the previous 5 years. As our understanding of pulmonary diseases changes, so will our approach to the imaging examinations. It is a fascinating area of radiology, and I encourage the radiologist to keep a watchful eye on the upcoming literature. I sincerely hope that you find this approach helpful with your current understanding of pulmonary diseases and in your daily work environment.

T

Oregon Health & Science University Department of Radiology Mail code: L340 3181 S.W. Sam Jackson Park Road Portland, OR 97201-3098 Phone: (503) 494-9000 Fax: (503) 494-4982 E-mail: [email protected] Copyright 2002, Elsevier Science (USA). All rights reserved. 0887-2171/0272304-0001535.00/0 doi..l O.lO53/sult.2002.36528 372

A CATEGORICAL APPROACH TO THORACIC IMAGING

1. Focal/Multifocal Consolidations

Acute Symptoms Pneumonia: Bacterial infections Mycoplasma Varicella.

Pulmonary edema: Hydrostatic and capillary leak (including acute respiratory distress syndrome [ARDS]).

Pulmonary hemorrhage: Focal--pulmonary embolus, contusions, Wegener's granulomatosis, and cocaine-induced hemorrhage/infarcts Diffuse--Pulmonary renal syndromes and inflammatory vasculopathies such as Goodpastures, Wegener's granulomatosis, systemic lupus erythematosus, and capillaritis.

Chronic Symptoms ("ANG10") Alveolar proteinosis Neoplasm: lymphoma and bronchioloalveolar cell carcinoma

Granulomatosis: tuberculosis/fungal and alveolar sarcoidosis

Inflammatory: bronchiolitis obliterans organizing pneumonia (BOOP) eosinophilic pneumonia, Churg-Strauss Old: chronic aspiration and lipoid pneumonia (Adenopathy makes lymphoma and granulomatosis most likely) 2. Ground Glass Opacities

Acute Symptoms Pneumonia: PCP: non-HIV often more acute presentation than HIV Cytamegalovirus or evolving and resolving bacterial infections. Pulmonary edema: Capillary leak ARDS, and acute interstitial pneumonitis (AIP) more common than hydrostatic edema. Pulmonary hemorrhage: Especially the inflammatory vasculopathies and capillaritis. Hyaline membrane disease: premature newborn.

Seminars in Ultrasound, CT, and MRI, Vol 23, No 4 (August), 2002: pp 372-374

THORACIC IMAGING

373

5. Nodular Pattern

Chronic Symptoms No to mild imaging evidence of fibrosis: Alveolar proteinosis Subacute hypersensitivity pneumonitis: extrinsic allergic alveolitis (nonsmoker) or drug-induced Desquamative interstitial pneumonia (DIP)/respiratory bronchiolitis-interstitial lung disease (RB-ILD) (Smoker) Cellular NSIP (overlaps with DIP, Hypersensitivity pneumonitis and occasionally BOOP) Lymphocytic interstitial pneumonitis (LIP) and follicular bronchiolitis: uncommon, but consider in collagen-vascular diseases and immunocompromised patients. Moderate to Severe imaging evidence of fibro-

sis:

Metastasis: any tumor Granulomatosis diseases Sarcoidosis Tuberculosis Fungal: histo, cocci, crypto, blasto Eosinophilic granuloma (Ill-defined nodules-smoker) Inhalation diseases Subacute hypersensitivity pneumonitis (III-defined nodules--nonsmoker) Silicosis, coal miner's pneumoconiosis, berylliosis Miliary Nodules: Granulomatous--TB, fungal, and sarcoid Metastasis--Thyroid, renal, breast, and melanoma.

6. Multiple-Cavitary Nodules/Masses

Usual interstitial pneumonitis (UIP): asbestosis, collagen vascular disease and occasionally drug induced. (Note: ground glass opacities without much imaging fibrosis likely represent an earlier phase of UIP) Honeycombing supports the diagnosis. Fibrotic nonspecific interstitial pneumonia: drug induced or collagen vascular etiologies most common. Honeycombing usually not a dominant imaging finding. Chronic hypersensitivity pneumonitis

3. Diffuse Reticular Opacities (Septal Thickening) Pulmonary edema: especially cardiogenic Lymphangitic spread of tumor: Adenocarcinoma and lymphoma are most common Interstitial pneumonia: viral or mycoplasma

4. Peripheral Reticular Pattern (Lace-Like Network) UIP This pattern of injury is commonly secondary to the following: Idiopathic pulmonary fibrosis Collagen vascular diseases, especially rheumatoid and scleroderma Drugs, ie, BCNU, Bleomycin Asbestosis Complications: pulmonary artery hypertension, lung cancer, accelerated deterioration (ground glass)

Infectious Bacterial--septic emboli/multiple abscesses, TB, nocardia Fungal--Coccidioidomycosis or aspergillus

Neoplasm: Squamous-cell carcinoma (primary or secondary), sarcoma

Vasculitis: Wegener's granulomatosis, angiocentric lymphoma Trauma: Traumatic lung cyst/hematoma

7. Cystic (Central Curvilinear/Reticular) Pattern Severe honeycomb lung (end-stage fibrosis) Diffuse or central bronchiectasis Pulmonary cysts: Pulmonary Langerhan's cell histiocytosis (smoking history) Lymphocytic interstitial pneumonitis (collagen vascular disease and HIV) Pneumocystis carinii pneumonia Lymphangioleiomyomatosis Tuberous sclerosis

8. Upper-Lobe Diseases ("SET PARC") Sarcoidosis Silicosis EG (Smoker) Extrinsic allergic alveolitis (nonsmoker) TB (Always consider fungal) Fungal

374

MARC V. GOSSELIN

PCP (ground glass and/or cysts) Ankylosing spondylitis/NF1 (both uncommon) Radiation therapy Cystic fibrosis (bronchiectasis)

9. Peripheral Lung Disease ("EPIC SUBS") Eosinophilic pneumonia Infarct/hemorrhage Contusion Sarcoidosis (alveolar form) Usual interstitial pneumonitis (UIP) BOOP Septic emboli

10. Bronchovascular Distribution Aspiration (acute presentation) Sarcoidosis Lymphoma Kaposi's sarcoma

11. Large Unilateral Pleural Effusion Malignancy CT may demonstrate extension along mediastinal pleural surface Infection: usually Emphysema Hemothorax: trauma or Iatrogenic

12. Peripheral Wedge-Shaped Hemorrhage/Infarction Pulmonary embolus Wegener's granulomatosis Angio-invasive aspergillus (neutropenia) Cocaine-induced pulmonary hemorrhage/infract

Thin-Section CT Centrilobular Nodules (two forms)

Tree-in-bud:--bronchopneumonia aspiration, mycoplasma,

endobronchial spread of TB, mycobacterium avium intercelularis (MAI), diffuse panbronchiolitis, allergic bronchopulmonary aspergillosis, Cystic fibrosis, Asthma, BOOP (early) III-defined Ground Glass Nodules: Extrinsic allergic alveolitis (nonsmoker), RB-ILD/DIP (smoker), LIP, and follicular bronchiolitis (collagen vascular disease, HIV) (Note: TIB may demonstrate thick reticular and ill-defined 3-mm nodular opacities on the radiograph that do not extend to the pleural surface. Concurrent bronchial wall thickening is often present.)

Mosaic Lung Attenuation 1. Lucent Regions Abnormal (vessels are smaller in lucent areas): *Small Airways Disease: Air trapping present on expiration--asthma, cystic fibrosis, bronchiolitis obliterans, diffuse panbronchiolitis, and MAI. *Pulmonary artery hypertension: No air trapping Chronic hypoxia: sleep apnea, chronic bronchitis, UIP, cystic fibrosis, hronchiolitis obliterans. Occlusive/destructive: Chronic thromboembolic disease, emphysema, vasculitis, primary pulmonary arterial hypertension, talc injection, parasitic infestation. Chronic pulmonary venous hypertension: mitral stenosis, chronic congestive heart failure, pulmonary veno-occlusive disease. Increased Flow (Left --~ Right Shunt): ASD, VSD, PDA, and Atrioventricular septal defect. 2. Lucent Regions Normal (Vessels same size in all areas): ground glass opacity differential diagnosis