Pleural Effusion-Transudate

Etiology

Cardiovascular Disease

Pulmonary Disease

  • Atelectasis (see Atelectasis, [[Atelectasis]])
  • Hantavirus (see Hantavirus, [[Hantavirus]]): pleural fluid is transudative early in course (probably due to cardiac dysfunction), later becomes exudative
  • Pleural Amyloidosis (see Amyloidosis, [[Amyloidosis]]): although these have been reported to be transudates, most of these patients have cardiac amyloid and associated CHF
  • Pulmonary Veno-Occlusive Disease (see Pulmonary Veno-Occlusive Disease, [[Pulmonary Veno-Occlusive Disease]])
  • Sarcoidosis (see Sarcoidosis, [[Sarcoidosis]]): rarely presents as transudate

Renal Disease

Other Disease

  • Acute Pulmonary Embolism (PE) (see Acute Pulmonary Embolism, [[Acute Pulmonary Embolism]]): 20% of cases are transudative
  • Bone Marrow/Stem Cell Transplant (see Bone Marrow Transplant, [[Bone Marrow Transplant]]): most reported cases had severe acute or chronic graft vs host disease (see Graft vs Host Disease, [[Graft vs Host Disease]])
  • Hepatic Hydrothorax (see Hepatic Hydrothorax, [[Hepatic Hydrothorax]])
  • Hypothyroidism (see Hypothyroidism, [[Hypothyroidism]])
  • Inadvertent Central Venous Catheter (CVC) Placement Into Pleural Space (see Central Venous Catheter, [[Central Venous Catheter]]): pleural fluid will have characteristics of the infusate, so may appear to be transudative or exudative
  • Inadvertent Nasogastric (NG) Tube Placement Into Pleural Space (see Nasogastric Tube, [[Nasogastric Tube]]): pleural fluid will have characteristics of the infusate, so may appear to be transudative or exudative
  • Meig’s Syndrome (see Meig’s Syndrome, [[Meigs Syndrome]]): original description was that of a transudate (however, subsequent reports note that these are typically exudates)
  • Pregnancy (see Pregnancy, [[Pregnancy]]): small amounts of U/S-detected pleural effusion are a normal finding in pregnancy (unclear whether these are transudates or exudates)
  • Severe Hypoalbuminemia (see Hypoalbuminemia, [[Hypoalbuminemia]])
  • Subarachnoid-Pleural Fistula

Diagnosis-Pleural Fluid Criteria (see Pleural Effusion-General, [[Pleural Effusion-General]])

General Comments

  • LDH Ratio and Total Protein Ratio are Necessary from Light’s Criteria
    • The pleural LDH <66% criterion does not add more in discriminative value
  • Cut-Off Values for LDH and Total Protein Ratios: since there is not a discrete cut-off between values of LDH and total protein, the specified cut-off values give high sensitivity but lower specificity (ie: you will detect all true exudates, but you may misclassify some transudates as exudates, as in diuresed congestive heart failure cases)

Transudate (see Pleural Effusion-Transudate, [[Pleural Effusion-Transudate]])

  • LDH Ratio <0.6
  • Total Protein Ratio <0.5
  • Pleural LDH <66% of Upper Limit of Normal Range for Serum LDH
  • Pleural Cholesterol <55-60 mg/L
  • Pleural/Serum Cholesterol Ratio: normal
  • Serum-Pleural Albumin Gradient (SPAG) >1.2 g/dL
    • If fluid clinically appears to be a transudate and SPAG >1.2, but Light’s criteria suggest exudate, fluid can be assumed to be a transudate (albumin is lower MW than other proteins and crosses capillary walls more easily)

Exudate (see Pleural Effusion-Exudate, [[Pleural Effusion-Exudate]])

  • General Comments: pleural effusion is considered exudative if it meets any one of the following criteria, although LDH ratio and total protein ratio are the best criteria
  • LDH Ratio >0.6
  • Total Protein Ratio >0.5
  • Pleural LDH >66% of Upper Limit of Normal Range for Serum LDH
  • Pleural Cholesterol >55-60 mg/dL
  • Pleural/Serum Cholesterol Ratio: elevated
  • Serum-Pleural Albumin Gradient (SPAG) <1.2 g/dl
    • If fluid clinically appears to be a transudate and SPAG >1.2, but Light’s criteria suggest exudate, fluid can be assumed to be a transudate (albumin is lower molecular weight than other proteins and crosses capillary walls more easily)

References

  • Unexplained effusions: association with allogeneic bone marrow transplantation and acute or chronic graft-versus-host disease. Bone Marrow Transplant. 1996 Feb;17(2):207-11 [MEDLINE]