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

The occurrence of significant mediastinal lymphadenopathy together with ple ural effusion or empyema inevitably raises concern about the presence of in trathoracic malignancy or granulomatous disease. Lymph node enlargement may also occur when pneumonia is accompanied by a parapneumonic effusion or em pyema. Features that allow "benign" lymph node enlargement to be distinguis hed from malignant causes have not previously been determined. The present study aims to establish the CT characteristics of enlarged nodes in parapne umonic effusion. The appearances of mediastinal lymph nodes were recorded i n 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 m aximum). Seven patients had a single involved site, nine patients two sites and two patients three sites. The right paratracheal area was most commonl y involved and the subcarinal area contained the largest nodes. The presenc e 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 wi th parapneumonic effusion and that multiple sites may be involved. The degr ee of enlargement is moderate although lymphadenopathy of greater than 2 cm size should raise the possibility of other pathology.