Ultrasound Animal Challenge 2 – Answer

The correct answer to the question "Which pathology does the 'snake sign' describe?" is:

C) Thrombus in the right atrium originating from the IVC or femoral veins

The snake sign or snake-like thrombus is clearly a frightening pathology. Its name however comes from its appearance, which resembles that of a snake. The thrombus forms in the veins of the lower extremity or IVC and therefore has the shape of a snake. If it dislodges it will cause pulmonary embolism (or even worse paradox embolism). Along its path it is often caught in the right heart where it can be detected with echo. The following image shows such a snake thrombus in a transthoracic subcostal view.

Yours,
Thomas Binder and the 123sonography team