Pulmonary pneumatocele 2017-04-23T11:52:30Z See Figure 52 of Hansell DM, et al., Fleischner Society: glossary of terms for thoracic imaging. Radiology. 2008;246:697-722. Pulmonary pneumatocoele A pneumatocele is a thin walled, gas-filled space in the lung. It is most frequently caused by acute pneumonia, trauma, or aspiration of hydrocarbon fluid and is usually transient. The mechanism is believed to be a combination of parenchymal necrosis and check-valve airway obstruction. A pneumatocele appears as an approximately round, thin-walled airspace in the lung. Pulmonary cyst