Causes of transudative effusions | Comment |
Processes that always cause a transudative effusion | |
Atelectasis | Caused by increased intrapleural negative pressure |
Cerebrospinal fluid leak into pleural space | Thoracic spinal surgery or trauma and ventriculopleural shunts |
Heart failure | Acute diuresis can result in borderline exudative features |
Hepatic hydrothorax | Rare without clinical ascites |
Hypoalbuminemia | Edema liquid rarely isolated to pleural space |
Iatrogenic | Misplaced intravenous catheter into the pleural space; post Fontan procedure |
Nephrotic syndrome | Usually subpulmonic and bilateral |
Peritoneal dialysis | Acute massive effusion develops within 48 hours of initiating dialysis |
Urinothorax | Caused by ipsilateral obstructive uropathy or by iatrogenic or traumatic GU injury |
Processes that may cause a transudative effusion, but usually cause an exudative effusion | |
Amyloidosis | Often exudative due to disruption of pleural surfaces |
Chylothorax | Most are exudative effusions |
Constrictive pericarditis | Bilateral effusions |
Hypothyroid pleural effusion | From hypothyroid heart disease or hypothyroidism per se |
Malignancy | Usually exudative, but 3 to 10 percent transudative possibly due to early lymphatic obstruction, obstructive atelectasis, or concomitant disease (eg, heart failure) |
Pulmonary embolism | Most are exudative effusions |
Sarcoidosis | Stage II and III disease |
Superior vena caval obstruction | May be due to acute systemic venous hypertension or acute blockage of thoracic lymph flow |
Coronavirus disease 2019 (COVID-19) | Limited data profile the nature of pleural fluid in COVID-19-related pleural effusions, although transudative effusions have been reported |
Nonexpandable lung* | A result of remote or chronic inflammation |
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