Role of Chest Computed Tomography in Patients Hospitalized with Community-Acquired Complicated Parapneumonic Effusion or Empyema: Role of CT in Parapneumonic Effusion

Clinical characteristics of community-acquired primary pleural infection compared to postpneumonic pleural infection: a retrospective study

BACKGROUND

Data on the clinical features and treatment outcomes in patients with primary pleural infection (PI) are limited. This study aimed to investigate the clinical characteristics of these patients.

PATIENTS AND METHODS

In this retrospective study, patients with community-acquired PI, diagnosed based on pleural fluid analysis, were classified into postpneumonic and primary PI groups according to computed tomography (CT) findings. Clinical variables, microbiological data, and CT findings were compared between the two groups.

RESULTS

Approximately 28 % of patients with community-acquired PI presented as primary PI. Treatment success rates and in-hospital or 30-day mortality were comparable between the two groups. However, compared to the postpneumonic PI group, the primary PI group was significantly younger and had lower proportions of patients with Pneumonia Severity Index classes 4-5 and RAPID (Renal, Age, Purulence, Infection source, and Dietary factors) score >3. On CT scans, subpleural abscesses were present in less than half of the patients in the primary PI group, compared to most patients in the postpneumonic PI group. Pleural enhancement and extrapleural fat proliferation were more frequently observed in patients with primary PI than in those with postpneumonic PI. In the primary PI group, Streptococcus anginosus group was the most common pathogen, accounting for nearly half of the causative organisms.

CONCLUSIONS

Patients with primary PI had similar treatment outcomes compared to those with postpneumonic PI. However, different causative pathogens and radiologic findings of primary PI suggest a distinct pathogenesis of PI independent of pneumonia.

Impact of photon counting detector CT derived virtual monoenergetic images and iodine maps on the diagnosis of pleural empyema

PURPOSE

The purpose of this study was to evaluate the impact of virtual monoenergetic image (VMI) energies and iodine maps on the diagnosis of pleural empyema with photon counting detector computed tomography (PCD-CT).

MATERIALS AND METHODS

In this IRB-approved retrospective study, consecutive patients with non-infectious pleural effusion or histopathology-proven empyema were included. PCD-CT examinations were performed on a dual-source PCD-CT in the multi-energy (QuantumPlus) mode at 120 kV with weight-adjusted intravenous contrast-agent. VMIs from 40-70 keV obtained in 10 keV intervals and an iodine map was reconstructed for each scan. CT attenuation was measured in the aorta, the pleura and the peripleural fat (between autochthonous dorsal muscles and dorsal ribs). Contrast-to-noise (CNR) and signal-to-noise (SNR) ratios were calculated. Two blinded radiologists evaluated if empyema was present (yes/no), and rated diagnostic confidence (1 to 4; not confident to fully confident, respectively) with and without using the iodine map. Sensitivity, specificity and diagnostic confidence were estimated. Interobserver agreement was estimated using an unweighted Cohen kappa test. A one-way ANOVA was used to compare variables. Differences in sensitivity and specificity between the different levels of energy were searched using McNemar test.

RESULTS

Sixty patients (median age, 60 years; 26 women) were included. A strong negative correlation was found between image noise and VMI energies (r = -0.98; P = 0.001) and CNR increased with lower VMI energies (r = -0.98; P = 0.002). Diagnostic accuracy (96%; 95% CI: 82-100) as well as diagnostic confidence (3.4 ± 0.75 [SD]) were highest at 40 keV. Diagnostic accuracy and confidence at higher VMI energies improved with the addition of iodine maps (P ≤0.001). Overall, no difference in CT attenuation of peripleural fat between patients with empyema and those with pleural effusion was found (P = 0.07).

CONCLUSION

Low VMI energies lead to a higher diagnostic accuracy and diagnostic confidence in the diagnosis of pleural empyema. Iodine maps help in diagnosing empyema only at high VMI energies.