Although this is generally a rare condition, it is important to recognise it as it is usually caused by a much more common condition, a liver abscess. Thus for every animal with thrombosis of the vena cava, there will be many more with significant liver damage due to abscesses.
Cause
Most cases of thrombosis occur as a result of an abscess forming in the liver. The infection spreads from the liver to cause a localised infection in the vein that passes near the liver, the vena cava. The localised infection can then result in the development of a solid mass (a thrombus) in the vena cava.

The thrombus is made up of made up of clotted blood, dead white blood cells, bacteria and other cells. Once formed, these thrombi can detach from the lining of the vena cava (they are then called emboli) and are carried in the bloodstream through to smaller blood vessels, where they become stuck. The most common site is in the lungs. Emboli in the lungs result in chronic pneumonia and the development of multiple lung abscesses.
Symptoms

• Respiratory distress

• Chronic coughing

• Weight loss

• Pale mucous membranes

Treatment
Prognosis is poor, and as such cases are fatal. If treatment is attempted it includes antibiotics and supportive therapy.
Prevention
Control efforts include the reduction of the incidence of ruminal acidosis. If abscesses are found they should be treated immediately to minimise the risk of spread.