Appearance of the Nellix endoprosthesis on postoperative imaging: implications for patient and device surveillance

The Nellix stent graft has novel features that influence interpretation of imaging follow-up, in particular, the use of endobags that seal the aneurysm sac. The polymer within the endobags contains a small amount of contrast medium, which causes a predictable temporal change in appearances. Understanding of these features allows correct image evaluation. In this article, we review the appearance of Nellix on computed tomography, ultrasound, magnetic resonance imaging, and plain radiography. We describe the special considerations that are important to consider when reviewing imaging, including endobag position and seal, endobag configuration, endobag and polymer maturation, and endobag gas. Detection of complications is discussed, with suggestion of a follow-up protocol based on the authors' experience.