Take Home Point #1: If you see >5% mesothelial cells in the pleural fluid, tuberculosis is unlikely!
Take Home Point #2: Rheumatoid pleurisy is typically associated with a very low pleural fluid glucose level.
Mesothelial cells: If you see greater than 5% mesothelial cells in the pleural fluid, tuberculosis is unlikely!
If you see a low pleural fluid glucose:
– Rheumatoid pleurisy
– Complicated parapneumonic effusion or empyema
– Malignant effusion
– Lupus pleuritis
– Esophageal rupture
If you see a high pleural fluid amylase:
– acute pancreatitis
– chronic pancreatic pleural effusion
– esophageal rupture
The evolution of an exudate:
- The acute response to any pleural injury (infectious, immunologic, or malignant) is the attraction of neutrophils to the pleural space.
- Then, around 72 hours after injury, mononuclear cells enter the pleural space and become the predominant cells.
- The macrophage predominance is subsequently replaced by lymphocytes in effusions that persist for >2 weeks.
What does this tell me?
A neutrophil-predominant exudate should be expected when the patients present acutely with a pleural effusion (e.g. acute bacterial pneumonia, acute pulmonary embolism, acute pancreatitis).
Pleural effusions that are subacute or chronic (e.g. TB, malignancy) are associated with a lymphocyte predominance.