A lung cavity or pulmonary cavity is an abnormal, thick-walled, air-filled space within the lung. Cavities in the lung can be caused by infections, cancer, autoimmune conditions, trauma, congenital defects, or pulmonary embolism. The most common cause of a single lung cavity is lung cancer. Bacterial, mycobacterial, and fungal infections are common causes of lung cavities. Globally, tuberculosis is likely the most common infectious cause of lung cavities. Less commonly, parasitic infections can cause cavities. Viral infections almost never cause cavities. The terms cavity and cyst are frequently used interchangeably; however, a cavity is thick walled (at least 5 mm), while a cyst is thin walled (4 mm or less). The distinction is important because cystic lesions are unlikely to be cancer, while cavitary lesions are often caused by cancer.Diagnosis of a lung cavity is made with a chest X-ray or CT scan of the chest, which helps to exclude mimics like lung cysts, emphysema, bullae, and cystic bronchiectasis. Once an imaging diagnosis has been made, a person’s symptoms can be used to further narrow the differential diagnosis. For example, recent onset of fever and productive cough suggest an infection, while a chronic cough, fatigue, and unintentional weight loss suggest cancer or tuberculosis. Symptoms of a lung cavity due to infection can include fever, chills, and cough. Knowing how long someone has had symptoms for or how long a cavity has been present on imaging can also help to narrow down the diagnosis.
Pulmonary embolism and septic emboli
Pulmonary embolism (a blood clot in the lung) causes pulmonary infarction (the death of lung tissue) less than 15% of the time, and only about 5% of pulmonary infarctions result in lung cavities. Septic pulmonary emboli (infected blood clots) are collections of infectious organisms, fibrin, and platelets that travel through the blood to the lung and cause small areas of pulmonary infarction by blocking off blood flow. This results in multiple small cavities 85% of the time. Symptoms can include cough, dyspnea (shortness of breath), chest pain, hemoptysis (coughing up blood) and sinus tachycardia (a fast heart rate). Risk factors for septic pulmonary emboli include IV drug use, implanted prosthetic devices (like central lines, pacemakers, and right-sided heart valves), and septic thrombophlebitis (a blood clot in a vein due to infection). Two forms of septic thrombophlebitis include pelvic thrombophlebitis and Lemierres syndrome (septic thrombophlebitis of the internal jugular vein). Trauma
Pulmonary contusion (lung bruise) from blunt chest trauma causes bleeding into the alveoli (air sacs) and can cause small cavities to form that are called traumatic pulmonary pseudocysts (TPP). This is rare, as less than 3% of lung injuries lead to TPP. It can occur at any age, but is more common in children and adults under the age of 30. Although it can occur anywhere in the lung, it is most common in the lower lobes. TPP usually resolves on its own within four weeks.