Vena caval thrombosis and metastatic pneumonia is associated with multifocal abscesses in the lung as the result of septic embolism of the pulmonary arterial vascular system arising from septic thrombi in the caudal vena cava. The most common cause of vena caval thrombosis is ruminal acidosis leading to rumenitis and subsequent liver abscessation, which may result in a thrombus in the caudal vena cava if the vessel wall is infiltrated by the abscess. Bacteria most frequently involved include Fusobacterium necrophorum, Trueperella pyogenes, staphylococci, streptococci, and Escherichia coli.
The condition usually occurs in adult dairy cattle or in feedlot cattle on high-carbohydrate diets. Presenting signs can be acute, manifested by respiratory distress, or chronic, manifested by weight loss and chronic coughing. A common presentation is tachypnea, tachycardia, hemic murmurs, coughing, pale mucous membranes, increased lung sounds, hemoptysis, and epistaxis. Pyrexia and melena may also be present. The case fatality rate is essentially 100%.
A thrombus is found in the vena cava, and hepatic abscesses may be noted. A suppurative pneumonia is present with pulmonary abscesses, aneurysms, and blood clots from ruptured aneurysms found throughout the entire lung parenchyma. The generalized distribution of these lesions caused by hematogenous spread is characteristic of this condition.