Pulmonary emboli were once thought to cause transudative effusions, but have been recently shown to be exudative. The mechanism for the exudative pleural effusion in pulmonary thromboembolism is probably related to increased permeability of the capillaries in the lung, which results from the release of cytokines or inflammatory mediators (e.g. vascular endothelial growth factor) from the platelet-rich blood clots. The excessive interstitial lung fluid traverses the visceral pleura and accumulates in the pleural space.Conditions associated with transudative pleural effusions include:
Congestive heart failure
Liver cirrhosis
Severe hypoalbuminemia
Nephrotic syndrome
Acute atelectasis
Myxedema
Peritoneal dialysis
Meigss syndrome
Obstructive uropathy
End-stage kidney disease

Exudative
When a pleural effusion has been determined to be exudative, additional evaluation is needed to determine its cause, and amylase, glucose, pH and cell counts should be measured. Red blood cell counts are elevated in cases of bloody effusions (for example after heart surgery or hemothorax from incomplete evacuation of blood). Amylase levels are elevated in cases of esophageal rupture, pancreatic pleural effusion, or cancer. Glucose is decreased with cancer, bacterial infections, or rheumatoid pleuritis. pH is low in empyema (<7.2) and maybe low in cancer. If cancer is suspected, the pleural fluid is sent for cytology. If cytology is negative, and cancer is still suspected, either a thoracoscopy, or needle biopsy of the pleura may be performed. Gram staining and culture should also be done. If tuberculosis is possible, examination for Mycobacterium tuberculosis (either a Ziehl–Neelsen or Kinyoun stain, and mycobacterial cultures) should be done.
For patients with malignant pleural effusions, it allows them to continue chemotherapy if indicated. Generally, the tube is in for about 30 days, and then it is removed when space undergoes spontaneous pleurodesis. Tubercular pleural effusion is one of the common extrapulmonary forms of tuberculosis. Treatment consists of antituberculosis treatment (ATT). The currently recommended ATT regime is two months of isoniazid, rifampicin, ethambutol and pyrazinamide followed by four months of isoniazid, rifampicin and ethambutol. See also
Pleural disease
Empyema
Heart failure
Pulmonary embolism
Subpulmonic effusion
Thoracentesis

References
External links

MedlinePlus Encyclopedia: Pleural Effusion
Pleural Effusion Images from MedPix