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Infectious pulmonary nodules in immunocompromised patients: usefulness of computed tomography in predicting their
Tomás Franquet1, Nestor L Müller, Ana Giménez
1Department of Radiology, Hospital de Sant Pau, Universitat Autonoma de Barcelona, Avda. Sant Antoni Ma. Claret 167, 08025 Barcelona, Spain. 19429tfc@comb.es
Insights
Nodule size on high-resolution computed tomography (CT) can help differentiate infectious causes in immunocompromised patients. Nodules under 10 mm are most indicative of viral infections, aiding diagnosis.
Area of Science:
- Radiology
- Infectious Diseases
- Pulmonology
Background:
- Immunocompromised patients are susceptible to various pulmonary infections.
- Nodular opacities on imaging can represent diverse infectious etiologies.
- Distinguishing these infections based on imaging features is clinically important.
Purpose of the Study:
- To evaluate high-resolution computed tomography (CT) findings in immunocompromised patients with infectious pulmonary nodules.
- To determine if specific CT features can differentiate various infectious causes of pulmonary nodules.
Main Methods:
- Retrospective review of high-resolution CT scans from 78 immunocompromised patients with proven infectious nodules.
- Exclusion of cases with tree-in-bud patterns or endobronchial spread.
- Assessment of nodule presence, size, appearance, and distribution.
- Regression analysis to correlate CT findings with infectious etiology.
Main Results:
- Infectious causes included mycobacteria, fungi, bacteria, and viruses.
- Nodule diameter less than 10 mm was the sole independent predictor of etiology.
- Viral infections were strongly associated with nodules <10 mm (83% of cases).
- Bacterial, mycobacterial, and fungal infections showed lower frequencies of small nodules.
Conclusions:
- Nodule size on CT is a valuable, though not definitive, tool for diagnosing infectious pulmonary nodules in immunocompromised individuals.
- Patients with all nodules measuring <10 mm are highly likely to have a viral infection.
Purpose:
To review the high-resolution computed tomography (CT) findings in immunocompromised patients who had nodular opacities and a proven diagnosis to determine whether the various infectious pulmonary nodules have distinguishing features on CT.
Materials And Methods:
The high-resolution CT scans obtained in 78 immunocompromised patients with solitary or multiple nodular opacities of proven infectious etiology were reviewed retrospectively by 2 independent thoracic radiologists. Patients whose predominant abnormality consisted of branching linear or nodular opacities (tree-in-bud pattern) characteristic of infectious bronchiolitis and endobronchial spread of tuberculosis were excluded. The CT scans were assessed for the presence, appearance, size, and distribution of parenchymal nodules. Relations between findings at CT and the different infectious etiologies of nodules were assessed with regression analysis. Agreement between the 2 observers was assessed using the kappa statistic.
Results:
The infectious causes included mycobacteria (n = 24), fungi (n = 22), bacteria (n = 20), and viruses (n = 12). Multivariate analysis demonstrated that a diameter <10 mm was the only independent predictor of etiology (P < 0.0001) and that patients whose nodules all measured less than 10 mm in diameter were most likely to have a viral infection. Nodules limited in size to less than 10 mm in diameter were seen in 83% of viral infections compared with 5% of bacterial infections (odds ratio [OR] = 95.0; 95% confidence interval (CI): 6.08-4,321.5, P < 0.0001), 0% of mycobacterial infections (OR = 91.7; 95% CI: 7.21-4,090.22, P < 0.0001), and 14% of fungal infections (OR = 31.67; 95% CI: 3.56-375.09, P = 0.0003).
Conclusion:
Although some overlap exists, nodule size is helpful in the differential diagnosis of infectious causes of nodules in immunocompromised patients. Patients whose nodules are all less than 10 mm in diameter are most likely to have a viral infection.
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