Intrathoracic lymphadenopathy in patients with empyema

Radiographic Imaging of Community-Acquired Pneumonia: A Case-Based Review

The chest radiograph is the most common imaging examination performed in most radiology departments, and one of the more common indications for these studies is suspected infection. Radiologists must therefore be aware of less common radiographic patterns of pulmonary infection if they are to add value in the interpretation of chest radiographs for this indication. This review uses a case-based format to illustrate a range of imaging findings that can be associated with acute pulmonary infection and highlight findings that should prompt investigation for diseases other than community-acquired pneumonia to prevent misdiagnosis and delays in appropriate management.

Internal thoracic lymphadenopathy and pulmonary tuberculosis

OBJECTIVE

Internal thoracic lymphadenopathy (ITL) has been associated with malignancies and non-tuberculous empyema. However, the association between ITL and active pulmonary tuberculosis (PTB) and the correlation between ITL and other imaging characteristics of active PTB has not been examined.

MATERIALS AND METHODS

A retrospective cohort study comprising 137 adults with active PTB who had a concomitant chest CT over a seven-year period was conducted. Two thoracic radiologists evaluated for ITL as well as nine other imaging characteristics of active tuberculosis, including total lung involvement (as measured by a total severity score), number of nodules, presence of tree-in-bud nodularity, highest extent of tree-in-bud nodularity in a lobe, miliary pattern, cavitary lesions, pleural effusion, lymphadenopathy (excluding internal thoracic lymph nodes), and empyema. The Wilcoxon rank-sum test and chi-squared tests were used to assess the correlation between ITL and additional imaging findings.

RESULTS

Internal thoracic lymphadenopathy was present in 50 of 137 cases (36.5%); most commonly bilateral (19.0%) or isolated on the right side (13.7%), and less commonly isolated on the left side (3.7%). Pleural effusion, lymphadenopathy (apart from internal thoracic compartment), and empyema all showed statistically significant correlations with ITL (p-values of <0.0001).

CONCLUSIONS

While the presence of ITL - particularly when accompanied by other imaging findings such as pleural effusion - may prompt a radiologist to first consider malignancy, active PTB should be an additional consideration in the appropriate clinical context.

The characteristics and significance of thoracic lymphadenopathy in parapneumonic effusion and empyema

The occurrence of significant mediastinal lymphadenopathy together with pleural effusion or empyema inevitably raises concern about the presence of intrathoracic malignancy or granulomatous disease. Lymph node enlargement may also occur when pneumonia is accompanied by a parapneumonic effusion or empyema. Features that allow "benign" lymph node enlargement to be distinguished from malignant causes have not previously been determined. The present study aims to establish the CT characteristics of enlarged nodes in parapneumonic effusion. The appearances of mediastinal lymph nodes were recorded in 50 consecutive patients with parapneumonic effusion/empyema. 18 (36%) had mediastinal lymphadenopathy (node size greater than 1 cm). The mean number of enlarged nodes was 1.9 (range 1-3) and the mean size was 1.4 cm (2 cm maximum). Seven patients had a single involved site, nine patients two sites and two patients three sites. The right paratracheal area was most commonly involved and the subcarinal area contained the largest nodes. The presence of enlarged nodes did not correlate with biochemical and microbiological stage of pleural infection, length of history, or extent of consolidation. This study shows that mediastinal lymphadenopathy is commonly associated with parapneumonic effusion and that multiple sites may be involved. The degree of enlargement is moderate although lymphadenopathy of greater than 2 cm size should raise the possibility of other pathology.

Infection of the pleural space

Parapneumonic effusions are common accompaniments of pneumonia that require proper management to prevent progression to empyema. Management decisions require thoughtful individualization of care because of the multiple factors that affect outcome; no one algorithmic approach exists for all patients. Basic principles of care, however, apply to all patients and center on the early detection of infected pleural fluid and the rapid completion of effective pleural drainage and lung re-expansion, when indicated to decrease morbidity and mortality.