Obstructive shock caused by right atrial thrombosis secondary to malignant pheochromocytoma in a dog.

To the best of authors' knowledge, this is the first report of severe obstructive shock secondary to extension of caval tumour thrombus into the right atrium in a dog with malignant pheochromocytoma. Tumour thrombus from a malignant pheochromocytoma should be included as a differential diagnosis of obstructive shock, with or without a visible right intra-atrial mass, in dogs. Serial focused ultrasonography during intravenous fluid administration can aid diagnosis.