Stent

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In the technical vocabulary of medicine, a stent is an artificial '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.

Etymology

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.^[1] 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. It is worth noting that the first "stents" used in medical practice were initially called "Wallstents". In 1985, the Argentine doctor, Palmaz et al, create the self-expanding stent that is used until today.^[2]

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. Coronary stents are placed during a percutaneous coronary intervention procedure, also known as an angioplasty.	An example of a coronary stent. This version, known as a Taxus stent, has a drug-eluting function
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.	Example of a uretal stent used to alleviate hydronephrosis of the kidney
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[3] 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.[4] 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.	Example of a stent / catheter used in the prostate to treat an enlarged prostate and provide relief in cases of obstructed urination
Stents are used in a variety of blood vessels aside from coronary arteries. Stents may be used as a component of peripheral artery angioplasty.	Stents for peripheral vessels
Esophageal stent	Endoscopic image of a self-expanding metallic stent in an esophagus, used to palliatively treat esophageal cancer
Biliary stent, providing bile drainage	Endoscopic image of a biliary stent seen protruding from the ampulla of Vater at the time of duodenoscopy
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.	Example of a stent used in an endovascular aneurysm repair
Other types are duodenal stents, colonic stents, and pancreatic stents, the designations referring to the location of their placement.

See also

• Angioplasty
• Bronchoscopy
• Colonoscopy
• Esophagogastroduodenoscopy
• Grommet
• Interventional radiology
• Restenosis
• Bioresorbable stents

References

External links

Wikimedia Commons has media related to: [//commons.wikimedia.org/wiki/Category:Stent Stent]

• Coronary Stent
• Drug-Eluting Stents — Angioplasty.Org
• Cardiovascular and Interventional Radiological Society of Europe
• The Cardiovascular Forum
• Stent for Life Initiative