Congenital right atrial diverticulum in a kitten.

A four-month-old domestic shorthair cat with no clinical signs was referred for further examination of a heart murmur. An echocardiogram revealed marked right atrial dilation, extending into the left hemithorax. Computed tomography angiography was conducted to investigate further, which revealed a balloon-shaped, contrast-filled cavity on the cranial and left side of the chest that connected to the right atrium through a narrow passage. This was diagnosed as a congenital right atrial diverticulum. Treatment included clopidogrel to reduce the risk of thrombus formation. Two months after the initial diagnosis, castration surgery was successfully performed without complications. The cat died suddenly at home 10 months after diagnosis. To the authors' knowledge, this is the first right atrial diverticulum reported in a cat.