The air meniscus as a radiographic finding: a review of the literature and presentation of nine unusual cases.

In addition to echinococcal cysts and mycetomas, a wide variety of disorders can occasionally produce an air meniscus sign on a chest radiograph. A proposed classification follows: I. Infections A. Lung abscess (with or without pulmonary gangrene) B. Fungus ball C. Bacterial ball D. Tuberculoma E. Blood clot in tuberculous cavity, Rasmussen aneurysm F. Echinococcal lung cyst II. Neoplastic A. Bronchogenic carcinoma B. Primary lung sarcoma C. Metastatic carcinoma, sarcoma to lung D. Bronchial adenoma E. Cystic hamartoma III. Developmental A. Bochdalek hernia (pseudocavity) IV. Traumatic A. Pulmonary hematoma V. Hemodynamic A. Congestive heart failure (with or without bullae)