대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Actinomycosis

Radiologic Findings

CT scans show segmental consolidation in right upper lobe.
Delayed images shows tubular branching structures of low attenuation within the mildly-enhancing consolidation.

Brief Review

Actinomycosis is caused by members of the family Actinomycetaceae.
The most important cause of disease in humans is A. israelii.
This organism is characterized by its mycelial granules, which are usually called sulfur granules because of their yellow color.

The organisms are normal inhabitants of the human oropharynx, especially in persons with poor oral hygine.
In the majority of cases, disease is aquired by the direct spread of endogenous organisms from the oropharynx into the lung or into the gastrointestinal tract.
Most infections occur in individuals who are not immunocompromised.

Grossly, chronic pulmonary actinomycosis is characterized by multiple abscesses interconnected by granulating sinus tracts and surrounded by a variable amount of fibrous tissue.

Histologically, the abscesses are composed of an outer rim of grannulation tissue surrounding masses of polymorphonuclear leukocytes that often contain typical sulfur granules.
Surrounding lung parenchyma shows a variable degree of fibrosis and chronic inflammatory infiltrate.

The typical pattern in the acute variety of actinomycosis consists of airspace pneumonia, without recognizable segmental distribution, commonly in the periphery of the lung and with a predilection for the lower lobes.

With appropriate therapy, most cases resolve without complications.

Actinomycosis frequently presents roentgenographically as a mass that simulates pulmonary carcinoma.
According to the many articles and textbook, extension across the pleural fissures and into the chest wall is common. However, recent study for the radiologic findings of thoracic actinomycosis in SNUH (1) revealed that all 22 patients showed no evidence of chest wall involvement.


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Abstract of an article about CT findings of thoracic actinomycosis by Cheon et al (1)

PURPOSE: To characterize computed tomographic (CT) findings of thoracic actinomycosis.

MATERIALS AND METHODS:
Chest CT scans and radiographs obtained in 22 patients with histopathologically proved thoracic actinomycosis were retrospectively reviewed.
All patients were immunocompetent; they were aged 12-73 years (mean, 42.6 years; 14 male, eight female).
CT findings were correlated with histopathologic findings in nine patients who underwent surgery (lobectomy [n = 8] or segmental resection [n = 1]).

RESULTS:
All of the lesions were unilateral, with an average diameter of 6.5 cm (range, 2-12 cm).
Patchy air-space consolidation (n = 20) or a mass (n = 2) was seen on CT scans.
Fifteen (75%) of the 20 patients with air-space consolidation had central areas of low attenuation (5-30 mm in diameter) within the consolidation.
Thirteen of the 15 patients underwent contrast medium-enhanced CT.
Ten (77%) of the 13 patients showed ring-like rim enhancement.
Adjacent pleural thickening was seen in 16 patients (73%).
At histopathologic examination, central low-attenuation areas at CT were seen as microabscesses with sulfur granules or a dilated bronchus that contained inflammatory cells and Actinomyces colonies.
Peripheral enhancement of the low-attenuation areas was wall of the microabscess or surrounding parenchyma composed of granulation tissue rich in vascularity.

CONCLUSION:
Findings of chronic segmental air-space consolidation that contained low-attenuation areas with peripheral enhancement or adjacent pleural thickening at CT were suggestive of thoracic actinomycosis.

References

1. Cheon J-E, Im J-G, Kim MY, Lee JS, Choi GK, Yeon KM. Thoracic actinomycosis: CT findings. Radiology 1998;209:229-233

Keywords

Lung, Infection, Bacterial infection,