If symptoms or imaging findings have been present for less than three months, the cause is most likely an acute infection; if they have been present for more than three months, the cause is most likely a chronic infection, cancer, or an autoimmune disease.The presence of lung cavities is associated with worse outcomes in lung cancer and tuberculosis; however, if a lung cancer develops cavitation after chemotherapy and radiofrequency ablation, that indicates a good response to treatment. Formal definition
In the 2008 Fleischner Society "Glossary of Terms for Thoracic Imaging", a cavity is radiographically defined as “a gas-filled space, seen as a lucency or low-attenuation area, within [a] pulmonary consolidation, a mass, or a nodule”. Pathologically, a cavity is “usually produced by the expulsion or drainage of a necrotic part of the lesion via the bronchial tree.”

Lung cavity mimics
The first step in evaluating a suspected lung cavity lesion is to exclude other kinds of abnormal air-filled spaces in the lung, including lung cysts, emphysema, bullae, and cystic bronchiectasis. Lung cysts are the most common mimics of lung cavities. Cavities and cysts are similar in that they are both abnormal, air-containing spaces with clearly defined walls. The difference between cavities and cysts is that cavities are thick walled, while cysts are thin walled.
Other urogenital problems may arise such as prostatitis in men and cervicitis, salpingitis and/or vulvovaginitis in women. It presents with monoarthritis affecting the large joints such as the knees and sacroiliac spine causing pain and swelling. An asymmetrical inflammatory arthritis of interphalangeal joints may be present but with relative sparing of small joints such as the wrist and hand. Patient can have enthesitis presenting as heel pain, Achilles tendinitis or plantar fasciitis, along with balanitis circinata (circinate balanitis), which involves penile lesions present in roughly 20 to 40 percent of the men with the disease. A small percentage of men and women develop small hard nodules called keratoderma blennorrhagicum on the soles of the feet and, less commonly, on the palms of the hands or elsewhere. The presence of keratoderma blennorrhagica is diagnostic of reactive arthritis in the absence of the classical triad. Subcutaneous nodules are also a feature of this disease. Ocular involvement (mild bilateral conjunctivitis) occurs in about 50% of men with urogenital reactive arthritis syndrome and about 75% of men with enteric reactive arthritis syndrome. Conjunctivitis and uveitis can include redness of the eyes, eye pain and irritation, or blurred vision. Eye involvement typically occurs early in the course of reactive arthritis, and symptoms may come and go. Dactylitis, or "sausage digit", a diffuse swelling of a solitary finger or toe, is a distinctive feature of reactive arthritis and other peripheral spondylarthritides but can also be seen in polyarticular gout and sarcoidosis. Mucocutaneous lesions can be present.