Medicine – Causes of Cavitation on a Chest Radiograph

Pulmonary cavitation refers to an air-containing space within an area of lung consolidation, a pulmonary nodule, or a mass. It usually develops when lung tissue undergoes necrosis and then drains into the bronchial tree. Important causes include infection, malignancy, vascular disease, occupational lung disease, inflammatory disorders, and advanced fibrotic lung disease.

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1. Bullae

Pulmonary bullae are thin-walled, air-filled spaces caused by destruction and enlargement of distal air spaces, most often in association with emphysema. They are not true necrotic cavities, but they may resemble cavitary lesions on a chest radiograph.

Large bullae can compress adjacent normal lung and may rupture, occasionally leading to a spontaneous pneumothorax.

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2. Cavitating Pneumonia

Certain bacterial pneumonias can cause necrosis of lung tissue and subsequent cavitation. Important organisms include Klebsiella species, Staphylococcus aureus, and anaerobic bacteria.

Anaerobic infection is particularly associated with aspiration, while staphylococcal pneumonia can produce multiple areas of necrosis, abscess formation, or pneumatoceles.

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3. Pulmonary Tuberculosis

Tuberculosis is a classic cause of pulmonary cavitation, especially in post-primary or reactivation TB. Cavities are often found in the upper lobes and may have irregular walls.

Cavitary TB is clinically important because these lesions may contain a high concentration of organisms, making the patient potentially highly infectious.

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4. Lung Abscess

A lung abscess is a localised collection of pus caused by necrosis and destruction of lung tissue. When the abscess communicates with a bronchus, an air–fluid level may be visible on an erect chest radiograph.

Aspiration is an important cause, particularly in patients with impaired consciousness, swallowing difficulty, or poor dental hygiene.

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5. Tumour

Certain lung tumours may undergo central necrosis and cavitate. Squamous cell carcinoma is the primary lung cancer most classically associated with cavitation.

Pulmonary metastases can also occasionally cavitate. A thick-walled or irregular cavity should therefore raise suspicion of malignancy, particularly in an older patient or someone with a smoking history.

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6. Pulmonary Embolism

A pulmonary embolism can occasionally cause pulmonary infarction. If the infarct undergoes necrosis, cavitation may develop, although this is relatively uncommon.

Pulmonary infarction more commonly appears as a peripheral pleural-based opacity before any cavitation occurs.

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7. Pneumoconiotic Nodule

Occupational lung diseases such as silicosis and coal workers’ pneumoconiosis can produce large fibrotic nodules or masses. These lesions may occasionally cavitate.

In a patient with silicosis, the development of cavitation should also raise concern for superimposed tuberculosis, because silica exposure increases susceptibility to TB.

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8. Rheumatoid Nodule

Patients with rheumatoid arthritis may develop pulmonary rheumatoid nodules, particularly in severe seropositive disease.

These nodules may undergo central necrosis and cavitation. Infection and malignancy should still be excluded because they can produce a similar radiographic appearance.

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9. Granulomatosis with Polyangiitis

Granulomatosis with polyangiitis, formerly called Wegener’s granulomatosis, is a necrotising granulomatous vasculitis affecting mainly the respiratory tract and kidneys.

It commonly causes multiple pulmonary nodules or masses, and these lesions may cavitate. Other features may include sinus disease, haemoptysis, haematuria, and glomerulonephritis.

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10. Eosinophilic Granulomatosis with Polyangiitis

Eosinophilic granulomatosis with polyangiitis, formerly called Churg–Strauss syndrome, is a small-vessel vasculitis associated with asthma and eosinophilia.

Pulmonary infiltrates are common, but true cavitation is not a typical feature. If marked cavitation is present, alternative diagnoses such as granulomatosis with polyangiitis, infection, or malignancy should be considered.

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11. Honeycomb Lung

Honeycombing is seen in advanced pulmonary fibrosis and consists of multiple clustered, usually subpleural cystic air spaces caused by severe architectural distortion of the lung.

These spaces may look like multiple small cavities on imaging, but they are fibrotic cystic spaces rather than true necrotic cavities. High-resolution CT is much better than a plain chest radiograph for demonstrating this pattern.

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Key Clinical Pattern

Important causes of a cavitary appearance on chest imaging include tuberculosis, necrotising pneumonia, lung abscess, and cavitating squamous cell carcinoma.

Multiple cavitating nodules may suggest granulomatosis with polyangiitis, metastatic malignancy, septic embolic disease, or rheumatoid nodules, while bullae and honeycombing are important structural mimics of true cavitation.