In medicine, a stent is a tube usually constructed of a metallic alloy or a polymer. It is inserted into the lumen of an anatomic vessel or duct to keep the passageway open. Stenting refers to the placement of a stent. The word "stent" is also used as a verb to describe the placement of such a device, particularly when a disease such as atherosclerosis has pathologically narrowed a structure such as an artery.