ISSN 2398-2993      



Ben Dustan

Vetstream Ltd

Synonym(s): Pleural effusion


  • Hemothorax describes free blood within the pleural cavity with a packed cell volume (PCV) similar or higher than that obtained from a blood sample.
  • Hemomediastinum describes blood contained within the mediastinum and can occur in conjunction with or separately from a hemothorax.
  • Cause: wide variety of causes including trauma, neoplasia, hemostatic dysfunction/coagulopathy. Majority of reported cases in cattle appear to be traumatic, exceptions being cases in neonates which are frequently related to hemostatic dysfunction/coagulopathies, be these acquired or hereditary.
  • Signs: muffled heart and lung sounds on thoracic auscultation, hypovolemic shock, dyspnea/respiratory distress/tachypnea, lethargy, cyanosis, malaise.
  • Diagnosis:
    • History.
    • Clinical examination.
    • Thoracocentesis (PCV and TP of fluid).
    • Radiography.
    • Hematology and biochemistry (including PCV, TP, electrolytes, urea and creatinine), clotting/coagulation profile.
    • Ultrasonography.
  • Treatment: therapeutic thoracocentesis with thoracic drainage to relieve dyspnea, specific treatment for identified underlying condition.
  • Prognosis: largely dependent on etiology - typically guarded.




  • The majority of blunt thoracic trauma cases do not develop hemothorax, but potentially serious bleeding can occur from damaged intercostal, internal thoracic or other vessels caused by the sharp ends of rib fractures.
  • Diaphragmatic rupture can also result in hemothorax in its acute stages.
  • Laceration of vessels or lung parenchyma by thoracic penetrating or gunshot wounds can result in hemothorax combined with pneumothorax.


  • Iatrogenic damage to the intercostal or internal thoracic vessels is a recognized risk and complication to any thoracotic surgery.
  • Tamponade (pressure build up) in the region of the bleeding vessel does not occur so clots do not form.
  • Incorrect thoracocentesis Thoracocentesis may also cause potentially serious hemothorax.

Hemostatic dysfunction

  • Secondary clotting cascade disorders involving the extrinsic, intrinsic or common clotting pathways can result in significant spontaneous or trauma induced hemothorax or hemomediastinum.
  • Causes of secondary clotting cascade abnormalities can include Warfarin/Coumarin poisoning Rodenticide poisoning, bracken poisoning Bracken fern poisoning, disseminated intravascular coagulation (DIC), liver failure, parasites, septic/endotoxic shock, and hemophilia.

Thoracic masses

  • Bleeding with or without effusion from primary or metastastatic masses within the lung parenchyma or thoracic wall can occur or hemomediastinum
  • Invasion of blood vessels by thyroid carcinoma.
  • Erosion of blood vessels by infectious processes causing thoracic abscesses should also be considered.

Esophageal foreign body

Mechanical vessel abrasion

  • Rib cartilaginous exostoses or malignant bone neoplasms have been reported as a potential cause of hemothorax in man due to the abrasive, irregular lesion rubbing on vessels during respiration.

Predisposing factors


  • Primary clotting disorders characterized by petechiae and ecchymoses are unlikely to result in significant spontaneous bleeding into body cavities. However, their inclusion on a differential list is warranted due to the risk of increased hemorrhage following trauma.


Hypovolemic shock

  • Acute loss of more than 10-20 % of circulating volume results in death without adequate hypovolemic shock therapy.
  • The volume available in the pleural cavity of cattle will accommodate enough blood to cause death from hypovolemia before tamponade builds to stop bleeding.


  • Anemia following trauma may be due to bleeding from intercostal or other thoracic vessels. The hemorrhage is often self-limiting if not severe enough to cause rapid exsanguination.
  • Anemia is a common finding with other causes of slow intrathoracic hemorrhage including coagulopathies.


  • As for any pleural effusion, hemothorax can cause dyspnea and tachypnea due to the reduction in lung volume.

Pleuritis/pericarditis Pericarditis

  • Hemoglobin is a recognized adjuvant for the development of septic peritonitis and has the potential to exacerbate intra-pleural infectious processes.
  • The presence of chronic hemothorax can cause pleural and pericardial reaction and fibrosis leading to secondary clinical effects linked with these processes.


  • Rapid hemorrhage will result in acute collapse.
  • Chronic hemorrhage can result in onset of signs over days.


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Further Reading


Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Lee J R, Rosser T G & Cooley J (2016) Pulmonary embolization of immature Fascioloides magna casuing fatal hemothorax confirmed by molecular techniques in a heifer in the United States. J Vet Diagn Invest 28 (5), 584-8.
  • Trosch L, Mueller K, Brosinski K & Braun U (2015) Hemoabdomen and hemothorax in a cow with metastatic granulosa cell tumor. Schweiz Arch Tierheilkd 157 (6), 339-43 PubMed.

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