# Ultrasound Animal Challenge 2 – Answer

## Metadata
- Content type: Blog
- Canonical URL: https://123sonography.com/blog/ultrasound-animal-challenge-2-answer
- Published: September 19, 2022
- Last updated: July 2, 2024

## Overview
The snake sign or the snake-like thrombus forms in the veins of the lower extremity or IVC and therefore has the shape of a snake.

## Snapshot
- Category: Case

## Authors
- [Univ. Prof. Dr. Thomas Binder](/speaker/146) - Medical University of Vienna and founder/CMO 123Sonography, Webinar Moderation

## Tags
- Echo

## Related Courses
- [Echo BachelorClass](/course/echobachelorclass)

## Content
The correct answer to the question "[Which pathology does the 'snake sign' describe?](https://123sonography.com/blog/ultrasound-animal-challenge-2-snake-sign)" is:

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

[![](https://123sonography.com/sites/default/files/styles/video_thumbnail/public/video/images/snake-sign1.png?itok=eyrg9B9b)](https://vimeo.com/751202613&title=0&byline=0&portrait=0)

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.

[![](https://123sonography.com/sites/default/files/styles/video_thumbnail/public/video/images/snake-sign2.png?itok=QImoT7Il)](https://vimeo.com/751204322&title=0&byline=0&portrait=0)

**Yours,**
**Thomas Binder and the 123sonography team**