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In the technical vocabulary of medicine, a stent is a mesh 'tube' inserted into a natural passage/conduit in the body to prevent or counteract a disease-induced, localized flow constriction. The term may also refer to a tube used to temporarily hold such a natural conduit open to allow access for surgery.
The origin of the word "stent" remains unsettled. The verb form "stenting" was used for centuries to describe the process of stiffening garments (a usage long obsolete, per the Oxford English Dictionary) and some believe this to be the origin. According to the Merriam Webster Third New International Dictionary, the noun evolved from the Middle English verb stenten, shortened from extenten, meaning to stretch, which in turn came from Latin extentus, past participle of extendere, to stretch out. Others attribute the noun "stent" to Jan F. Esser, a Dutch plastic surgeon who in 1916 used the word to describe a dental impression compound invented in 1856 by the English dentist Charles Stent (1807–1885), whom Esser employed to craft a form for facial reconstruction. The full account is described in the Journal of the History of Dentistry. According to the author, from the use of Stent's compound as a support for facial tissues evolved the use of a stent to hold open various bodily structures. The first (self expanding) "stents" used in medical practice in 1986 by Ulrich Sigwart in Lausanne were initially called "Wallstents". Julio Palmaz et al. created a balloon expandable stent that is currently used.
Though many doctors have created the stent, the first FDA approved stent was invented by Gary S. Roubin.
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|The most common use for stents is in coronary arteries, into which a bare-metal stent, a drug-eluting stent, a bioabsorbable stent, a dual-therapy stent (combination of both drug and bioengineered stent), or occasionally a covered stent is inserted.|
|Ureteral stents are used to ensure the patency of a ureter, which may be compromised, for example, by a kidney stone. This method is sometimes used as a temporary measure to prevent damage to a blocked kidney until a procedure to remove the stone can be performed. Indwelling times of 12 months or longer are indicated to hold open ureters which have been compressed by tumors in the neighbourhood of the ureter or by tumors of the ureter itself. In many cases, these tumors are inoperable and the stents are used to ensure drainage of urine through the ureter. If drainage is compromised for longer periods, the kidney can be damaged. The main complications with ureteral stents are dislocation, infection, and blockage by encrustation. Recently, stents with coatings (e.g., heparin) have been approved to reduce infection, encrustation, and, therefore, the frequency of stent replacement.|
|A urethral or prostatic stent might be needed if a man is unable to urinate. This situation often occurs when an enlarged prostate pushes against the urethra, blocking the flow of urine. The placement of a stent can open the obstruction. Recent scientific breakthroughs have confirmed the use of a prostatic stent as a viable method of disobstructing the prostate. Stents can be temporary or permanent. Temporary stents can be placed in a urologist's office in a manner similar to placing a Foley catheter, requiring less than 10 minutes and using only lidocaine jelly as a local anesthetic. Clinical results show the temporary stent is effective and well tolerated. Permanent stents are mostly placed on an outpatient basis under local or spinal anesthesia and usually take about 30 minutes to insert. Clinical results show occurrences of migration, painful wearing, and difficult removal.|
Prostatic/sphincter stents can be used for draining the bladder in patients with urethra obstruction or damage to the nerves controlling the bladder. Stents can be placed in the prostate, across the outer and inner sphincter, to achieve good drainage of the bladder. The patient requires diapers, incontinence pants/plastic pants, or an external collection device (external catheter) to collect the urine.
|Stents are used in a variety of blood vessels aside from coronary arteries. They may be used as a component of peripheral artery angioplasty. Common sites treated with peripheral artery stents include carotid, iliac, and femoropoliteal arteries. Because of the external compression and mechanical forces subjected to these locations, flexible stent materials such as nitinol are used in a majority of peripheral stent placements.|
|Biliary stent, providing bile drainage|
|A stent graft is a tubular device composed of special fabric supported by a rigid structure, the stent, which is usually metal. An average stent on its own has no covering, and is usually just a metal mesh. |
The device is used primarily in endovascular surgery. Stent grafts support weak points in arteries; such a point is commonly known as an aneurysm. Stent grafts are most commonly used to repair an abdominal aortic aneurysm, in a procedure called an EVAR. The theory behind the procedure is that once in place inside the aorta, the stent graft acts as a false lumen through which blood can travel, instead of flowing into the aneurysm sack.
Stent grafts are also commonly placed within grafts and fistulas used for dialysis. These accesses can become obstructed over time, or develop aneurysms similar to those in other blood vessels. A stent graft can be used in either situation to create an open lumen and prevent blood from flowing around it.
|Glaucoma drainage stents are recent developments and are awaiting approval in some countries. They are used to reduce intraocular pressure by providing a drainage channel.|
|Other types are duodenal stents, colonic stents, and pancreatic stents, the designations referring to the location of their placement.|
|The neutrality of this section is disputed. (April 2014)|
In 2007 the New England Journal of Medicine published the results of a trial called COURAGE. The trial gave recommendations about the practice of stenting in PCI, a heart intervention. This study was recognized as strong evidence for the need for a field-wide change in practice.
Medical societies recommend that surgeons not perform stenting in the usual surgery of otherwise healthy individuals during percutaneous coronary intervention. A report by the Chicago Tribune also noted that the use of cardiac coronary artery stents was too high in cases where the patient was in at least stable condition and the coronary artery stent(s) was implanted on an elective basis—many times more than one is implanted in the same procedure, even in the same vessel. However, the report was careful to note that they are indisputably still a viable therapy that often produces satisfactory results for those with acute coronary artery disease, such as relief of an arterial occlusion that has caused a heart attack (myocardial infarction), or where there is a danger of a piece of the blockage detaching and traveling (a thrombosis) to occlude a vessel in the cardiopulmonary system or the brain.
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