Cavities in the lungs are formed by inflammation of lung tissue leading to the development of an abscess. When the abscess ruptures, the contents are expectorated, leaving behind an air- and fluid-filled cavity. Chest X-rays and computer tomography, or CT, scans can detect lung cavitations. Several infections and diseases cause lung cavitation.
Tuberculosis, periodontal disease and necrotizing pneumonia are bacterial causes of lung cavities. Tuberculosis is a disease caused by infection with the mycobacterium tuberculosis. The infection can cause the formation of granulomas, which is a protective response by the body. In granulomas, immune system cells collect in order to destroy the invading pathogen. Sometimes the granulomas can become abscesses that lead to lung cavitation. Bacteria found in the oral cavity--most often with periodontal disease--can be aspirated into the lungs where they cause an abscess. Necrotizing pneumonia, a rare disorder that can cause rapid lung cavitation, is caused by bacteria normally found in hospital. Even more rarely, certain fungi of the genus Aspergillus cause lung cavitation.
Sarcoidosis and Wegener's granulomatosis are inflammatory diseases that can cause the formation of cavities in the lungs. Like tuberculosis, these diseases cause formation of granulomas in the lungs. The Merck Manuals Online Medical Library reports that sarcodosis is most common in African Americans and those of Scandinavian descent, and that Wegener's granulomatosis in most often observed in Caucasians. Both diseases are rare and tend to affect people younger than 40.
Bronchiectasis can be caused by recurrent lung infections and inflammation, which ultimately lead to irreversible damage of the airways in the lungs. The Merck Manuals Online Medical Library states that CT scans of patients with bronchiectasis are characterized by "tramlines" that depict thickening of the airways and cysts that may be associated with cavitation.
Tumors that have arisen in the lungs or that have metastasized to the lungs can cause lung cavitation by obstructing the airways and leading to mucus accumulation in pockets of the lungs. Bacteria sometimes can infect these areas behind the tumors and form an abscess. A study published in the "Journal of Vascular and Interventional Radiology" reported that lung cavitation can also occur in patients that have had their tumors ablated.
A pulmonary embolism results when a blood clot from another area in the body travels through the bloodstream and blocks a pulmonary artery. A study in the journal "Chest" reported that blood clots that contain bacteria can lodge in the arteries of the lungs and cause an abscess that leads to cavitation.