The Pulmonary Air Meniscus

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Abstract
Sporadically, there have been recorded in the literature cases in which chest roentgenograms disclosed a rounded pulmonary density surmounted by a crescent-shaped air shadow. The appearance of this roentgenographic image is sufficiently characteristic that various investigators have considered it as a radiologic sign, describing it under a variety of terms, such as la calotte aérienne, neumoquiste perivesicular, halo claro lineal, air cap, and air crescent (1). Inasmuch as it has the configuration of a convergent meniscus, this air shadow may be referred to as the sign of the pulmonary air meniscus. A review of the literature reveals that this radiologic finding is not a pathognomonic one, since it has been demonstrated in a limited number of pulmonary disorders. Nevertheless, with careful correlation of clinical and roentgen observations, it is frequently possible to establish a correct diagnosis. In view of the fact that most of the reports of the pulmonary air meniscus have appeared in the foreign literature, it was considered worth while to present the following three cases in which this singular roentgenographic finding was demonstrated to advantage. The significance of this phenomenon with reference to those conditions in which it may occur will be briefly discussed. Case I: A 24-year-old colored male was admitted to the Grady Memorial Hospital in 1942 with a one-week history of hemoptysis, chills, fever, night sweats, and right chest pain. Blood cultures were negative and sputum examination showed no evidence of acid-fast organisms. The chest roentgenogram obtained a few days after admission showed an abscess cavity in the right upper lobe surrounded by a rather homogeneous area of consolidation (Fig. 1). The patient improved clinically on sulfathiazole therapy, and the x-ray examination ten days later demonstrated considerable clearing of the process, with disappearance of the cavity (Fig. 2). Roentgen studies several weeks after the original admission again disclosed a small cavity, which now contained a small rounded density in its base (Fig. 3). Three months later the patient was readmitted to the hospital because of progressively increasing productive cough, night sweats, and right chest pain. Bronchoscopy at this time demonstrated an erythematous carina, with exudate coming from the right upper lobe bronchus. Both the cavity and the rounded mass in its base had increased in size (Fig. 4). A crescent-shaped air shadow surmounting the area of density was well visualized on the film shortly before exploratory thoracotomy (Fig. 5). The pathologic examination of the surgical specimen showed a chronic abscess of the right upper lobe containing inspissated debris. No ephithelial lining of the cavity wall was demonstrated. Case II: A 42-year-old white woman was admitted to the Emory University Hospital in 1947, complaining of a “lump in the throat.”
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