Canis ISSN: 2398-2942
Pleural: effusion
Contributor(s): Yvonne McGrotty, Elizabeth Rozanski
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:
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
Diagnosis
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Treatment
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- Smeak D D, Stephen J, Birchard S J, McLoughlin M A et al (2001) Treatment of chronic pleural effusion with pleuroperitoneal shunts in dogs 14 cases (1985-1999). JAVMA 219 (11), 1590-1597 PubMed.
- Clikenbeard K D (1992) Diagnostic cytology - carcinomas in pleural fluid. JAAHA 14, 187-195 AGRIS FAO.
- Stowater J L & Lamb C L (1989) Ultrasonography of noncardiac thoracic disease in small animals. JAVMA 195 (4), 514-520 PubMed.
- Forrester S D, Troy G C & Fossum T (1988) Pleural effusions - pathophysiology and diagnostic considerations. Comp Cont Ed Pract Vet 10 (2), 121-136 VetMedResource.
- Myer W (1978) Radiography review - pleural effusion. J Am Vet Rad Soc 19 (3), 75-79 Wiley Online Library.
Other sources of information
- Murphy K & Papasouliotis K (2011) Pleural effusions in dogs and cats 1. Diagnostic investigation. In Practice 33, 462-469.