What is a fully covered oesophageal stent?

A fully covered esophageal stent is a type of stent that has a membrane or covering that fully encases the metal mesh of the stent.  Some key points about fully covered esophageal stents:

- Covering - The stent is wrapped in a thin, flexible material such as silicone or polyurethane.  This covering prevents tissue ingrowth into the stent. 

- Removability - The full covering allows the stent to be relatively easily collapsed and removed later if needed.  Uncovered or partially covered stents become embedded and are not removable. 

- Migration - The smooth outer surface makes migration (unwanted movement) of the stent more likely compared to uncovered stents. 

- Tissue irritation - The covering helps prevent the metal mesh from irritating the esophageal lining, making it more comfortable. 

- Usage - Fully covered stents are typically used for benign (non-cancerous) esophageal conditions like strictures or fistulas where retrievability is desired. 

- Patency - The covering can make the inner diameter slightly narrower, which can increase the chances of foods getting stuck during swallowing. 

 Overall, the main advantages of fully covered esophageal stents are removability and reduced tissue ingrowth and irritation.  The tradeoff is they may have higher migration rates and less radial force compared to uncovered metal mesh stents.