대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Legionnaires' disease

Radiologic Findings

Initial chest radiograph (CPA 1) shows large homogeneous consolidations in RLL and LUL. Follow-up chest radiograph (CPA 2), obtained 5 days after CPA 1, shows rapid progression of those consolidations into cavitary lesions with thick nodular wall. Chest CT scans (CT 1 & 2) show mass-like periphral consolidations and bilateral pleural effusion.

Brief Review

Legionnaires' disease is caused by Legionella pneumophilia; an aerobic gram-negative bacillus found in aquatic environments such as reservoirs, cooling towers, water distribution systems, and humidifiers. Predisposing chronic diseases are common and may be either pulmonary or systemic. Corticosteroid therapy is a recognized risk factor.
The initial chest radiographic finding is peripherally situated patchy consolidation, which spreads rapidly, often involving more than one lobe and becoming bilateral in half the cases, often despite the institution of appropriate antibiotic therapy. The consolidations may assume a spherical configuration or may coalesce to resemble lobar pneumonia. There may be a slight predilection for the lower lobes. In immunocompetent patients, abscess formation and subsequent cavitation is infrequent, but cavitation is seen fairly frequently in immunocompromised patients. The interval between the first evidence of infection and cavitation ranges from 4 to 14 days. Pleural effusions, which are usually small but occasionally massive, are documented in up to two thirds of cases at the peak of the illness, and frank empyema formation may occur. Hilar or mediastinal lymph node enlargement is not a feature of Legionnaires' disease. With appropriate therapy, roentgenographic resolution may be fairly rapid but is often prolonged. The changes may persist for at least a month after the acute illness. The organism is difficult to culture from sputum and blood, and selective culture media are required. The diagnosis is usually established serologically by an indirect fluorescent antibody test. In this case, diagnosis was made by culture from percutaneous needle aspiration of lung lesion and indirect immuno-fluorescence antibody test for Legionella pneumophilia.

References

1. Armstrong P, Wilson AG, Dee P, Hansell DM. Imaging of diseases of the chest, 2rd ed. Mosby, 1995:159-160
2. Evans AF, Oakley RH, Whitehouse GH. Analysis of the chest radiograph in Legionnaire's disease. Clin Raiol 1981;32:361-365

Keywords

Lung, Infection, Bacterial infection,