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Algorithmic Approach to Lung Opacities

Brett M. Elicker, MD

University of California, San Francisco

Approach to lung opacities

• This is hard!

• You will not be an expert today

• Approach

• Practice

• Think like a pathologist

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Categories of lung opacities

• 1. Consolidation

• 2. Interstitial

• 3. Airways

• 4. Other

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Alveolar

Interstitial

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Airways

Not applicable

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Consolidation

• Confluent opacity

• Fluffy around periphery

• Air bronchograms

• Lack of volume loss

Confluent opacity, no volume loss

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Air bronchograms

Consolidation

• Acute vs. chronic symptoms

• Distribution

• Acuity of changes

• Differential diagnosis in acute setting

– Edema

– Acute lung injury

– Infection

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2 month f/ubaseline

Invasive mucinous adenocarcinoma

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Comparison

Signs of atelectasis: volume loss

Fissuredisplacement

Elevateddiaphragm

Deviation ofmediastinalstructures

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Nodules Lines

Interstitial opacities

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Nodules: diff dx

• Hematogenous spread

– Miliary tuberculosis

– Miliary fungal infection (e.g. cocci)

– Metastases

• Lymphatic spread

– Sarcoidosis

– Lymphangitic spread of tumor

– Pneumoconioses (e.g. silica)

Histoplasmosis

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Miliary tuberculosis

Interstitial: lines

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Causes of interstitial lines

• Edema

• Malignancy

• Fibrotic lung diseases (this

is a long list)

Kerley-b lines may be present

These lines are typicallythick, wavy and irregular

Linear opacities

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Pulmonary edema (kerley-b lines)

Edema: alveolar + interstitial

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Reticular opacities (distribution)

• Mid-lower lobe predominant

– Idiopathic pulmonary fibrosis

– Connective tissue disease

– Drugs

– Asbestosis

– Hypersensitivity pneumonitis

• Upper lobe predominant

– Sarcoidosis

– Prior TB/fungus

– Pneumoconioses

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Idiopathic pulmonary fibrosis

Hypersensitivity pneumonitis

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Tuberculosis

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Airways disease

• Circular

• Tubular

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Differential diagnosis of airways disease

• Mild:

– Asthma

– Viral infection

– Chronic bronchitis

– Etc.

• Severe:

– Bronchiolitis obliterans

– Immunodeficiency

– Ciliary dyskinesia

– Cystic fibrosis

– ABPA

– Tuberculosis

– Cartilage diseases

Cystic fibrosis

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Which compartment of lung is affected?

Solitary pulmonary nodule: differential diagnosis

• Granuloma

• Hamartoma

• Primary bronchogenic carcinoma

• Metastasis

• Lots of others

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Nodules: benign vs. malignant

Benign Malignant

Small size Large size

Smooth border Spiculated border

Diffuse calcificationNo or irregular calcification

Stability over time Growth over time

Nodule: size

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Nodule: calcification

Nodule borders

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So you see a nodule on CXR…

• 1. Is it actually a nodule?

? nodule

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Shallow obliques

? nodule

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Apical lordotic

So you see a nodule on CXR…

• 1. Is it actually a nodule?

• 2. Look for prior films?

• 3. Is diffuse calcification present?

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Dual energy subtraction x-ray

So you see a nodule on CXR…

• 1. Is it actually a nodule?

• 2. Look for prior films?

• 3. Is diffuse calcification present?

• 4. Get a CT scan or a follow-up CXR

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Category Subcategory CXR features Common causes

Alveolar•Confluent opacities•Air bronchograms

•Fluffy edges

•Edema•Acute lung injury

•Infection

Interstitial

Nodules•Small, well‐defined nodules•Opacities not confluent

•Normal lung between nodules

•Tuberculosis•Fungal infection

•Metastases•Sarcoidosis

Lines(kerley‐b)

•Thin, fine, delicate lines•Lines at periphery of lung 

(kerley‐b)

•Pulmonary edema•Cancer

Lines (reticular)

•Thick, wavy, irregular lines•Fibrotic lung 

disease

Airways•Circular or tubular•Thin or thick walled

•Numerous causes

Not in a single compartment

•One or a few nodules (≤3 cm) or masses (>3 cm)

•Lung cancer•Metastasis•Granuloma•Hamartoma

Not all cases are straightforward

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Well-defined: interstitial

Ill-defined: alveolar

Extensive nodules: interstitial

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Peribronchial cuffing: interstitial

Airways: circles and tubes

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Algorithmic Approach to Lung Opacities

Brett M. Elicker, MD

University of California, San Francisco