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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.
Stent types 
|Type and description||Illustration|
|The most common use for stents is in coronary arteries, into which a bare-metal stent, a drug-eluting 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 dis-obstructing 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 that 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. Stents may be used as a component of peripheral artery angioplasty.|
|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. Although there are many types of stents, these stents are used mainly for vascular interventions.
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.
|Other types are duodenal stents, colonic stents, and pancreatic stents, the designations referring to the location of their placement.|
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.
See also 
- Interventional radiology
- Bioresorbable stents
- Ring, Malvin (2001). "How a Dentist's Name Became a Synonym for a Life-saving Device: The Story of Dr. Charles Stent". Journal of the History of Dentistry 49 (2): 77–80. PMID 11484317.
- Palmaz JC, Sibbitt RR, Reuter SR, Tio FO, Rice WJ. Expandable intraluminal graft: a preliminary study. Work in progress. Radiology. 1985 Jul;156(1):73–77.[PubMed]
- Dineen MK, Shore ND, Lumerman JH, Saslawsky MJ, Corica AP (May 2008). "Use of a temporary prostatic stent after transurethral microwave thermotherapy reduced voiding symptoms and bother without exacerbating irritative symptoms". Urology 71 (5): 873–7. doi:10.1016/j.urology.2007.12.015. PMID 18374395.
- Kural AR, Tüfek I, Akpinar H, Gürtuğ A (November 2001). "Removal of urolume endoprosthesis using holmium:YAG laser". J. Endourol. 15 (9): 947–8. doi:10.1089/089277901753284198. PMID 11769852.
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- Fay Corte, Michelle (26 March 2007). "Stents Fail to Cut Deaths, Heart Attacks in New Study (Update5)". bloomberg.com. Retrieved 6 September 2012.
- Husten, Larry (September 4, 2012). "ESC Trials: The Best And The Worst - Forbes". forbes.com. Retrieved September 6, 2012.
- WINSTEIN, KEITH J. (11 Feb 2011). "Why Health Policies Can Fail to Keep Up With Key Medical Findings". The Wall Street Journal (New York: Dow Jones). ISSN 0099-9660. Retrieved 6 September 2012.
- American College of Cardiology, "Five Things Physicians and Patients Should Question", Choosing Wisely: an initiative of the ABIM Foundation (American College of Cardiology), retrieved August 17 2012
- Patel, M. R.; Dehmer, G. J.; Hirshfeld, J. W.; Smith, P. K.; Spertus, J. A.; American College of Cardiology Foundation Appropriateness Criteria Task Force; Society for Cardiovascular Angiography Interventions; Society Of Thoracic, S. et al. (2009). "ACCF/SCAI/STS/AATS/AHA/ASNC 2009 Appropriateness Criteria for Coronary Revascularization". Journal of the American College of Cardiology 53 (6): 530–553. doi:10.1016/j.jacc.2008.10.005. PMID 19195618.
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