Caudal vena cava thrombosis

Etiology

• Septic emboli released from liver abscess results in metastatic chronic suppurative bronchopneumonia and subsequent involvement of pulmonary blood vessels.
• Most common bacteria include: Fusobacterium necrophorum Fusobacterium necrophorum, Trueperella pyogenes, Staphylococci Staphylococcus spp, Streptococci Streptococcus spp, and Escherichia coli Escherichia coli.
• Less commonly, vena caval thrombosis can be caused by emboli from inflammatory processes in other organs such as the udder, uterus or claws.
• Umbilical infection is suspected to be a cause of vena caval thrombosis in calves.

Predisposing factors

• Most commonly affects adult dairy cattle.
• Ruminal acidosis Ruminal acidosis is the usual underlying cause of liver abscessation.

Pathophysiology

• Low ruminal pH (subacute ruminal acidosis, SARA) leads to rumenitis, erosion and ulceration of the ruminal epithelium.
• Bacterial colonize the papillae, leak into the portal circulation and cause liver abscesses.
• Septic emboli are released from liver abscesses and travel via the caudal vena cava to the lungs.
• It has been proposed that increased intra-abdominal pressure (e.g. pregnancy, parturition) may lead to focal narrowing of the caudal vena cava, making thrombus formation more likely at this site. There is some evidence that Fusobacterium necrophorum (commonly present in abscesses) may possess virulence factors promoting platelet aggregation, which may be a first step towards thrombus formation at this site.
• The bacteria proliferate in lung tissue and cause a suppurative bronchopneumonia.
• Invasion and erosion of pulmonary vessels in the latter stages of disease results in intrapulmonary or intrabronchial hemorrhage (seen as hemoptysis or epistaxis).
• Less commonly, it is possible that bacteraemia resulting from any septic focus could lead to caudal vena cava thrombosis.

Timecourse

• Typically, cattle demonstrate signs of respiratory disease for variable period (few days to months) prior to the development of other signs.
• Death typically results 7 days after the animal begins to to cough up blood, but can be sudden in the event of involvement and erosion of major pulmonary vessel.