Segmental Aplasia and Right Azygos Continuation of the Caudal Vena Cava in a Cat (Felis catus).

Segmental aplasia of the caudal vena cava is a rare variant, primarily reported in dogs. We describe herein a cat with this anomaly. The caudal vena cava was formed by confluence of the right and left common iliac veins and a common trunk of the right and left renal veins. The caudal vena cava continued to the right azygos vein and joined into the cranial vena cava. A confluence of hepatic veins drained into the right atrium as in the normal caudal vena cava. Detailed reports of venous variations are important for providing appropriate veterinary care.