A self-expandable metallic stent (or SEMS) is a metallic tube, or stent , used in order to hold open a structure in the gastrointestinal tract in order to allow the passage of food, chyme, stool, or other secretions required for digestion. SEMS are inserted by endoscopy, wherein a fibre optic camera is inserted either through the mouth or retrograde through the colon, in order to reach an area of narrowing. As such, it is termed an endoprosthesis. SEMS can also be inserted using fluoroscopy where  an X-ray image is used to guide insertion, or used as an adjunct to endoscopy. Composition and structure Schematic of self-expandable metallic stent used to treat vascular abnormalities Self-expandable metallic stents are cylindrical in shape, and are devised in a number of diameters and lengths to suit the application in question. They typically consist of cross-hatched, braided or interconnecting rows of metal that are assembled into a tube-like structure. SEMS, when unexpanded, are small enough to fit through the channel of an endoscope, which is meant for delivery of devices for therapeutic endoscopy. They expand through a deployment device which is placed at the end of the SEMS, and are held in place against the wall of the luminal surface by friction. Applications The primary application of SEMS is in the palliation of tumours that obstruct the gastrointestinal tract. When they expand within the lumen, they are able to hold open the structure and allow passage of material, such as food, stool, or other secretions. The usual applications are for cancers of the esophagus, pancreas, bile ducts and colon that are not amenable to surgical therapy. SEMS may be used to treat additional complications of cancer, such as tracheoesophageal fistulas that may result from esophageal cancer, and gastric outlet obstruction which may result from stomach, duodenal  or pancreatic cancer. Esophageal SEMS are placed after a gastroscopy is performed to identify the area of narrowing. The area may need to be dilated in order to allow the gastroscope to pass. The tumour is usually better seen with the direct vision of endoscopy than on a fluoroscopic image. As a result, radio-opaque markers are usually placed on the surface of the patient in order to mark the area of narrowing on fluoroscopy. The SEMS is placed through the channel of the endoscope into the esophagus over a guidewire, marked on fluoroscopy, and mechanically deployed (using a device that sits outside of the endoscope) such that it expands when in position. Hypaque or other water-soluble dye may be placed through the passage to ensure patency of the stent on fluoroscopy. Enteric and colonic SEMS are inserted in a similar fashion, but in the duodenum and colon respectively.
A self-expandable metallic stent (or SEMS) is a metallic tube, or stent that holds open a structure in the gastrointestinal tract to allow the passage of food, chyme, stool, or other secretions related to digestion. Surgeons insert SEMS by endoscopy, inserting a fibre optic camera — either through the mouth or colon— to reach an area of narrowing. As such, it is termed an endoprosthesis. SEMS can also be inserted using fluoroscopy where the surgeon uses an X-ray image to guide insertion, or as an adjunct to endoscopy. Composition and structure Schematic of self-expandable metallic stent used to treat vascular abnormalities Self-expandable metallic stents are cylindrical in shape, and are devised in a number of diameters and lengths to suit the application in question. They typically consist of cross-hatched, braided or interconnecting rows of metal that are assembled into a tube-like structure. SEMS, when unexpanded, are small enough to fit through the channel of an endoscope, which is meant for delivery of devices for therapeutic endoscopy. They expand through a deployment device placed at the end of the SEMS, and are held in place against the wall of the luminal surface by friction. Applications The primary application of SEMS is in the palliation of tumours that obstruct the gastrointestinal tract. When they expand within the lumen, they are able to hold open the structure and allow passage of material, such as food, stool, or other secretions. The usual applications are for cancers of the esophagus, pancreas, bile ducts and colon that are not amenable to surgical therapy. SEMS are used to treat additional complications of cancer, such as tracheoesophageal fistulas from esophageal cancer, and gastric outlet obstruction from stomach, duodenal , or pancreatic cancer. Esophageal SEMS are placed after a gastroscopy is performed to identify the area of narrowing. The area may need to be dilated to allow the gastroscope to pass. The tumour is usually better seen with the direct vision of endoscopy than on a fluoroscopic image. As a result, radio-opaque markers are usually placed on the surface of the patient to mark the area of narrowing on fluoroscopy. The SEMS is placed through the channel of the endoscope into the esophagus over a guidewire, marked on fluoroscopy, and mechanically deployed (using a device that sits outside of the endoscope) such that it expands when in position. Hypaque or other water-soluble dye may be placed through the passage to ensure patency of the stent on fluoroscopy. Enteric and colonic SEMS are inserted in a similar fashion, but in the duodenum and colon respectively.
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