Canis ISSN: 2398-2942

Lung: pulmonary thromboembolism

Contributor(s): Jana Gordon


  • Occlusion of pulmonary blood vessel by clot or embolus.
  • Cause: cardiac disease, neoplasia, disseminated intravascular coagulopathy (DIC), sepsis, many systemic diseases, idiopathic.
  • Signs: acute onset respiratory distress, tachypnea.
  • Diagnosis: angiography, arterial blood gas analysis, ventilation/perfusion scan.
  • Treatment: oxygen therapy, anticoagulant, treat underlying cause.
  • Prognosis: guarded to poor.




  • Occlusion of pulmonary vasculature by clot or embolus.
  • Clot formation requires one or more of the following: hypercoagulable state, vascular stasis or damage to the vascular endothelium.
  • Clot usually forms as a result of disease in organs other than lungs.
  • Various mechanisms of clot formation, eg:
    • Hyperadrenocorticism Hyperadrenocorticism increases concentrations of clotting factors, causes vascular changes and sometimes, platelet changes.
    • Glomerular diseases result in urinary loss of antithrombin, decreased fibrinolysis and platelet hypersensitivity associated with hypoalbuminemia.
    • Hemolytic anemia may cause release of thromboplastic substances from erythrocytes.
    • IV catheters.
    • Cardiac disease, eg DCM → vascular stasis within the heart.
    • Neoplasms often have abnormal vascular endothelial surfaces which can cause vascular stasis or activate the coagulation cascade.
  • Clot/embolus formation → occlusion of pulmonary vessels → ventilation perfusion mismatch → hypoxemia Hypoxemia.
  • Pulmonary hypertension Pulmonary Arterial Hypertension (PHT) may result due to obstruction or reflex vasoconstriction. Vasoactive substances and/or vagal reflexes may cause bronchoconstriction and increased airway resistance.


  • Acute.
  • Occasionally more chronic.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Johnson L R, Lappin M R & Baker D C (1999) Pulmonary thromboembolism in 29 dogs: 1985-1995. JVIM 13 (4), 338-345 PubMed.
  • Dennis J (1993) Clinical features of canine pulmonary thromboembolism. Comp Cont Ed Pract Vet 15 (12), 1595-1603 VetMedResource.
  • Keyes M L, Rush J E, Knowles K E (1993) Pulmonary thromboembolism in dogs. Vet Emerg & Crit Care 3 (1), 23-32 VetMedResource.
  • Dennis J S (1991) The pathophysiological sequelae of pulmonary thromboembolism. Comp Cont Ed Pract Vet 13, 1811-1818 AGRIS FAO.
  • LaRue M J, Murtaugh R J (1990) Pulmonary thromboembolism in dogs 47 cases (1987-1989). JAVMA 197 (10), 1368-1372 PubMed.
  • Klein M K, Dow S W, Rosychuk R A W (1989) Pulmonary thromboembolism associated with immune-mediated haemolytic anaemia in dogs: ten cases (1982-1987). JAVMA 195 (2), 246-250 PubMed.
  • Koblik P D, Hornoff W, Harnagel S H, Fisher P E (1989) A comparison of pulmonary angiography, digital subtraction angiography and 99MTc-DTPA/MAA ventilation-perfusion scintigraphy for detection of pulmonary emboli in the dog. Vet Rad 30 (4), 159-168 Wiley Online Library.

Other sources of information

  • Ettinger S G (2004) Textbook of Veterinary Internal Medicine. Saunders.
  • Lesley G King (2004) Textbook of Respiratory diseases in Dogs and Cats. Saunders.