Assessment of Mediastinal Lymph Node Size in Pneumococcal Pneumonia with Bacteremia

The significance of mediastinal lymphadenopathy in bacterial pneumonia is unclear.

We performed a retrospective analysis of mediastinal lymph node size determined by chest CT in patients with bacteremic pneumococcal pneumonia. All patients who had positive blood cultures for streptococcus pneumonia over an 11-year period and had a chest CT scan (index CT) within 2 weeks of the positive blood culture were included in the study. Two thoracic radiologists and one pulmonologist independently examined the index CT plus any chest CT scans performed prior (pre-CT) or after (post-CT) the bacteremic episode.

The study cohort of 49 patients was 57% male, 65% White, with mean age of 53 (SD = 20) years. Mediastinal lymphadenopathy was detected in 25/49 (51%) of the cases. The mean size of the largest mediastinal lymph node in short axis was 0.99 (SD = 0.71), ranging from 0.0 to 2.05 cm. There was no correlation noted between the number of lobes involved with pneumonia, and the size of the largest mediastinal lymph node (p = 0.33) or the number of pathologically enlarged mediastinal lymph nodes (p = 0.08). There was a statistically significant increase in the mean size of the largest lymph node between the pre-CT and index-CT group (p = 0.02), and decrease between the index-CT group and the post-CT (p = 0.03).

Pneumococcal pneumonia with bacteremia is associated with mild mediastinal lymph node enlargement. The presence of marked mediastinal lymphadenopathy (short axis LN size > 2 cm) should not be assumed from pneumococcal pneumonia.