Introduction

• Accumulation of fluid within the pleural cavity.
• Cause: fluid may be blood, chyle, exudate, transudate or modified transudate.
• Signs: respiratory distress related to reduced lung volume (tachypnea, dyspnea).
• Diagnosis: ultrasonography, radiography and thoracocentesis.
• Treatment: thoracocentesis and treatment of underlying cause where possible.
• Prognosis: guarded overall, uncommonly cured but may be successfully managed.

Pathogenesis

Etiology

• Fluid type reflects underlying pathophysiology:
  • Neoplasia (pulmonary Lung: pulmonary neoplasia , lymphosarcoma Lymphoma , mesothelioma Mesothelioma , or thoracic wall).
  •  Thorax: trauma(bite wound, RTA (HBC - hit by car), ruptured thoracic duct).
  • Cardiac disease → right sided heart failure Heart: congestive heart failure.
  • Pericardial disease Pericardial disease. Resulting in right-sided CHF Heart: congestive heart failure.
  • Foreign body Airway foreign body. Resulting in pyothorax Pyothorax.
  • Coagulopathy - especially anti-coagulant rodenticides Anticoagulant rodenticide poisoning.
  • Pneumonia resulting in pleuritis Pleuritis (pleuropneumonia).

Pathophysiology

• Accumulation of fluid within the pleural space by a variety of mechanisms → reduced lung volume → respiratory compromise.

Hemorrhage

• Trauma, anticoagulant rodenticide Anticoagulant rodenticide poisoning or neoplasia bleeding into pleural cavity.
• PCV of effusion is similar to that of blood and has similar white cell number.
• Usually doesn't clot due to rapid loss of fibrin (in contrast to inadvertant aspiration from blood vessel or heart).

Chyle

• Thoracic duct rupture is currently considered a RARE cause of chylothorax Chylothorax.
• True chylous effusion is usually caused by abnormal or obstructed lymph channels:
  • Lymphangectasia.
  • Idiopathic.
  • Inflammation or obstruction of flow, eg neoplasia, right-sided heart failure.

Exudate

• Introduction of bacteria into pleural space, eg bite wound, foreign body, esophageal perforation Esophagus: perforation , extension from pneumonic lung Lung: bacterial pneumonia.
• Migration of WBCs → pleural cavity, ie pyothorax Pyothorax or inflammatory conditions affecting pleura, eg neoplasia, immune-mediated disease or chylothorax Chylothorax.

Transudate

• Due to imbalance of absorption and filtration of fluid across pleura.
• May be due to:
  • Increased hydrostatic pressure.
  • Negative intra-pleural pressure, eg severe upper airway obstruction.
  • Reduction in resorption of fluid due to reduced lymphatic permeability or obstruction, eg immune-mediated disease, inflammatory or infectious conditions, eg uremia Uremia , pancreatitis Pancreatitis: acute , trauma, neoplasia, bacterial, viral and fungal infections.

Modified transudate

• Long-standing transudates which have increased protein and cells secondary to pleural inflammation.

Timecourse

• Acute to chronic.

Diagnosis

Treatment

Outcomes