Pulmonary Legionellosis in Oncologic Patients: Findings on Chest CT.

Objective: The purpose of this study was to report the computed tomography (CT) findings of non-pneumophila Legionella pneumonia and to compare these CT findings to those caused by Legionella pneumophila in oncologic patients.

Methods: Chest CT scans of 34 oncologic patients with culture-proven Legionella infection (16 L. pneumophila and 18 non-pneumophila Legionella) were retrospectively reviewed. Radiologic checkpoints included consolidation, ground-glass opacities, cavitation, nodules, tree-in-bud opacities, septal thickening, pleural effusions, and adenopathy, as well as the halo, reversed halo, and bulging fissure signs.

Results: The most common imaging feature of Legionella pneumonia was consolidation, seen in 94% of patients. Ground-glass opacities were the next most common abnormality. The halo sign was present in 26% of patients, in both immunocompetent and immunosuppressed hosts. Most features occurred with similar frequency between L. pneumophila and non-pneumophila Legionella.

Conclusions: Findings in L. pneumophila pneumonia and non-pneumophila Legionella pneumonia are similar but nonspecific. Airspace consolidation is almost always present; the halo sign is not uncommon.