Snapshot A 56-year-old woman presents to the emergency department due to worsening shortness of breath and cough. Her symptoms began yesterday after receiving peritoneal dialysis. She denies any productive cough, fevers, or chills. Medical history is significant for end-stage renal disease secondary to poorly controlled diabetes mellitus, requiring peritoneal dialysis. Physical exam is notable for a woman with increased work of breathing and decreased breath sounds over the right lower lobe. A chest radiograph is performed, which demonstrates an extensive right pleural effusion. Introduction Definition excessive fluid in the pleural space Etiology Transudative effusion left-sided heart failure cirrhosis nephrotic syndrome peritoneal dialysis atelectasis Exudative effusion bacterial pneumonia malignancy viral infection pulmonary embolism tuberculosis collagen vascular disorder Pathogenesis anatomy pleural fluid accumulation results when the formation of the pleural fluid exceeds its absorption pleural fluid enters the pleural space via capillaries within the parietal pleural interstitial spaces of the lung peritoneal cavity through holes in the diaphragm pleural fluid is removed from the pleural space via lymphatics in the parietal pleura disruption in any of these processes leads to the development of a pleural effusion effusions can be divided into transudative and exudative effusions transudative due to increased capillary pressure (e.g., congestive heart failure) or decreased plasma oncotic pressure (e.g., hypoalbuminemia) note, transudative pleural effusions result from alterations in systemic factors that affect the formation and absorption of pleural fluid exudative due to increased permeability of the pleural surfaces or impaired lymphatic reabsorption note, exudative pleural effusions result from alterations in local factors that affect the formation and absorption of pleural fluid Presentation Symptoms asymptomatic dyspnea on exertion peripheral edema Physical exam dullness to percussion decreased breath sounds on the effusion decreased tactile fremitus Imaging Radiography of the chest indication to determine the presence of a pleural effusion Studies Distinguishing transudative and exudative fluid requires the measuring of pleural and serum fluid levels lactate dehydrogenase (LDH) protein levels Thoracentesis with ultrasound guidance indication to collect pleural fluid in order to determine its etiology confirms the presence of pleural fluid Light criteria criteria used to differentiate transudative and exudative effusions protein (pleural)/protein (serum) > 0.5 LDH (pleura)/LDH (serum) > 0.6 LDH > 2/3rds the upper limit of normal serum LDH based on the Light criteria, a pleural effusion is said to be exudative if any of the above is met Treatment Depends on the underlying cause e.g., if there is an exudative effusion secondary to a bacterial pneumonia, treat with antibiotics Procedural therapeutic thoracentesis indication in cases where the pleural effusion is massive and its affecting the patient's breathing tube thoracostomy indication in complicated parapneumonic effusions or empyema Complications Parapneumonic effusion Empyema Prognosis Depends on the cause of the pleural effusion