stent

n.

a tube placed inside a duct or canal to reopen it or keep it open. It may be a simple tube, usually plastic, or an expandable, usually sprung mesh metal, tube. The former is more easily removable, while the latter gives a larger lumen for a given outer diameter. Stents may be used at operation to aid healing of an anastomosis, for example of a ureter. Alternatively they can be placed across an obstruction to maintain an open lumen, for example in obstruction due to tumour in the oesophagus, stomach, bile ducts, colon, or ureter. In an artery after angioplasty, stents help to prevent restenosis (narrowing) and are increasingly used in coronary artery disease in place of coronary artery bypass grafting (see percutaneous coronary intervention). Drug-eluting stents are coronary stents coated with a drug that inhibits growth of the scar tissue responsible for recurrent restenosis.

Double J (or pig-tail) stents are slender catheters with side holes that are passed over a guide wire either through an endoscope or at open operation to drain urine from the kidney pelvis to the bladder, via the ureter. On removal of the guide wire both the upper and lower extremities of the stent assume a J-shape, hence preventing both upward and downward migration. They are commonly used to splint a damaged ureter and to relieve obstruction.