Long-term ultrasonographic and venographic study of the development of tarsal vein thrombosis in a cow.

The development of thrombosis of three tarsal veins in a cow was studied by repeated ultrasonographic and venographic examinations for nine months. The venous diameter, the echogenicity of the thrombi and the sequential venographic findings were evaluated. Initially, the thrombosed parts of the ramus cranialis and caudalis of the vena saphena lateralis and the ramus caudalis of the vena saphena medialis had greatly increased diameters and were not compressible. The thrombi appeared as poorly echogenic masses. Within five months, the diameters of the occluded veins had decreased to almost normal dimensions. The echogenicity of the thrombi diminished at their distal and proximal ends. The length of the thrombi was decreased by up to 6.5 cm. However, the thrombosed veins did not re-open. One year after diagnosis, the cow was culled and the persistence of the venous thromboses was confirmed.