Presentation
Hyperthyroidism.
Patient Data
![](https://prod-images-static.radiopaedia.org/images/45781490/b089ce470b2d1dd437980ba063e12f1d3867b10aab603c3aeb53562bf9387264_big_gallery.jpeg)
Deep to left thyroid lobe is a structure with an echogenic rim and dense posterior shadowing. There is mild mass effect on the posterior aspect of the left thyroid lobe.
![](https://prod-images-static.radiopaedia.org/images/45781517/1be1e9aadff941e03b52cf911a53f6_thumb.jpeg)
![This study is a stack](/packs/stack-YQKLCKBI.gif)
![](https://prod-images-static.radiopaedia.org/images/45781542/5fd1609f60a762ffdc3a30708e1b58_thumb.jpeg)
![This study is a stack](/packs/stack-YQKLCKBI.gif)
![](https://prod-images-static.radiopaedia.org/images/45781517/1be1e9aadff941e03b52cf911a53f6_big_gallery.jpeg)
Paratracheal air cyst to the left of the trachea at the level of the thoracic outlet. No connection to the trachea can be identified. This has mass effect on the left thyroid lobe, pushing it mildly anteriorly.
Case Discussion
The findings are indeterminate on ultrasound as a peripherally calcified mass could have a similar appearance, although comparison with prior imaging reveals the answer of an incidental paratracheal air cyst. This is also an example of an uncommon left-sided paratracheal cyst; the vast majority (97%) are right-sided.