Giant right atrial aneurysm associated with persistent left cranial vena cava in a cat.

A 10-month-old female spayed Scottish Fold was referred to cardiology for incidental radiographic cardiomegaly. Echocardiography was suspicious for a right atrial or right auricular aneurysm. The differential diagnosis also included peritoneal-pericardial diaphragmatic hernia, mass lesion (cyst, granuloma, or neoplasia), or cardiac malformation. A giant right atrial aneurysm associated with a persistent left cranial vena cava was subsequently confirmed with computed tomography.