What is a fully covered esophageal SEMS?

A fully covered esophageal SEMS stands for a fully covered esophageal self-expanding metal stent. Here are more details:

- Self-expanding - The stent is made from a shape memory alloy that allows it to be compressed and inserted through the esophagus while collapsed. Once in place, it expands to widen the esophagus.

- Metal - SEMS are most commonly made from materials like nitinol, an alloy of nickel and titanium. This allows radial force to keep the esophagus open.

- Fully covered - The stent has a complete layer or sleeve on the outside made of silicone or polyurethane. This covering prevents tumor ingrowth through the mesh stent walls.

 - Esophageal - The SEMS is designed specifically to be inserted in the esophagus. It can provide palliative treatment for open strictures or narrowing caused by esophageal cancer.

- Stent - This expandable tube-like device is inserted via endoscopy and expands to a wider diameter once in place. It maintains patency and opens the lumen of the esophagus. 

In summary, a fully covered esophageal SEMS uses a metal mesh design with an outer coating to keep the esophagus open when narrowed by cancer. The full coverage prevents tissue growth through the stent. It provides relief of swallowing difficulties caused by esophageal strictures.