What Is a Stent?

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A stent is a metal or plastic tube inserted into a blocked passageway to keep it open. Since their introduction in the late-1980s, stents have revolutionized the treatment of coronary artery disease and other diseases in which vital vessels or passageways are obstructed.

The practice of stenting has become fairly common and has allowed for the minimally invasive treatment of conditions that once required surgery. Even so, there are complications associated with stenting and times when they may not be the best option for everyone.

This article looks at the different types of stents used in medicine today. It also describes the general procedure and the possible risks and side effects of stenting.

A stent in a coronary artery, illustration
Stocktrek Images / Getty Images

Stents should not be confused with shunts. Shunts are similar in design but are used to connect two previously unconnected passageways.


The first stent was implanted into a patient's heart in Toulouse, France, in 1986. Since then, stents have been used in other organs, including the kidneys, colon, and esophagus. Recent innovations have even allowed for the use of stents in treating certain types of glaucoma.

There are different types of stents used to treat different medical conditions. These include:

  • Coronary stents: Used for treating coronary artery disease, these stents are used as part of a procedure known as angioplasty. Today, the vast majority of angioplasties involve a coronary stent.
  • Endovascular stents: These stents are commonly used to treat advanced peripheral artery disease (involving arteries other than the heart), cerebrovascular disease (involving the brain), and renal artery stenosis (involving the kidneys).
  • Ureteral stents: Used to treat or prevent the obstruction of urine from the kidneys, these stents are placed inside a ureter (the vessel that connects a kidney to the bladder) and can be as long as 11 inches in length.
  • Prostatic stents: Used to enable urination in males with an enlarged prostate, these stents overcome obstructions caused when the prostate gland compresses the urethra (the passage through which urine exits the body).
  • Colonic stents: Used to treat bowel obstructions, these stents are often used in people with advanced colon cancer or other causes of bowel blockage.
  • Esophageal stents: Often used in people with advanced esophageal cancer, these stents keep the esophagus (feeding tube) open so that the person can swallow soft foods and liquids.
  • Pancreatic and biliary stents: Used to drain bile from the gallbladder and pancreas to the small intestine, these stents are often used when a gallstone blocks a bile duct and triggers a potentially life-threatening condition known as cholangitis.
  • Micro-bypass stents: A recent innovation used in people with mild to moderate open-angle glaucoma, these stents are implanted by a microsurgeon to reduce intraocular pressure (pressure within the eye) and slow disease progression.

There are different stents designed for different parts of the body. The goal of all stents is to keep a passageway open in order to restore normal flow and function.


The procedures used to implant a stent differ depending on the type of stent. Whether made with coated metals or next-generation polymers, the stents are meant to expand once inserted and provide a stable opening that prevents future collapse.

There are several techniques commonly used for the placement of a stent:

  • Coronary or endovascular stents: Performed under regional anesthesia or mild sedation, the procedure involves the insertion of a tiny tube called a balloon catheter into a vein in the groin, arm, or neck. The catheter is tipped with the stent and fed to the site of the obstruction. After inflating the tube to widen the vessel, the balloon is deflated and retracted, leaving the stent behind.
  • Ureteral or prostatic stents: The placement of these stents involves a cystoscope (a thin tube equipped with a camera) that is fed through the urethra to the site of the obstruction. A tiny wire connected to the scope's tip helps guide the stent into the correct position. Local, regional, or general anesthesia may be used.
  • Colonic or esophageal stents: The placement of these stents is similar to that of a ureteral or prostatic stent but involves either a colonoscope (inserted into the anus to visualize the colon) or an endoscope (inserted into the mouth to visualize the esophagus). A balloon catheter is commonly used to widen narrowed passages.
  • Pancreatic or biliary stents: The placement of these stents is performed either with an endoscope or a percutaneous transhepatic cholangiography (PTC), in which a needle is inserted into the liver through the abdomen to place the stent. Monitored sedation or general anesthesia may be used.
  • Micro-bypass stents: The placement of these stents involves a tiny incision in the eye's cornea by an ophthalmologic microsurgeon. The tiny stent (roughly one millimeter in length and 0.3 millimeters in height) is positioned in a structure known as the Schlemm's canal that helps regulate the fluid balance of the eye.

Risks and Side Effects

As important as stents are to the treatment of many potentially serious conditions, they have their limitations and risks. Your doctor will weigh the benefits and risks to determine if you are a candidate for stenting.


One of the complications a doctor will watch out for after placing a coronary and endovascular stent is restenosis. Restenosis occurs when new tissue grows in a treated blood vessel, causing it to narrow.

While stents greatly reduce the risk of restenosis compared to angioplasty alone, the complication can still affect some people, usually within 12 months of their procedure.

The bare-metal stents developed in the early 1990s cut the risk of restenosis roughly by half. Today, stents are coated with chemotherapy or immunosuppressant drugs, which lowers the risk even more—to around 6%.

Another possible complication is late thrombosis. This is caused when injury to a vessel triggers the formation of blood clots a year or more after the procedure. To help avoid this potentially serious complication, anti-platelet drugs like Plavix (clopidogrel) may be prescribed to inhibit the formation of clots.

Possible side effects and complications of coronary stents include:

  • Chest pain, mainly due to restenosis
  • Arrhythmia (abnormal heart rhythms)
  • Return of the original symptom if the stent fails
  • Heart attack or stroke if thrombosis develops

Urinary Tract

Ureteral and prostatic stents can sometimes get blocked due to the buildup of mineral crystals from urine. The encrustation can be minimized by using drug-eluting stents coated with a blood thinner known as heparin. Heparin can also help reduce the risk of infection.

Many of the urinary side effects are temporary and will resolve on their own without treatment. These include:

  • Urinary frequency (the increased need to urinate)
  • Urinary urgency (a feeling you need to urinate constantly)
  • Bladder leakage
  • Kidney, bladder, or groin pain
  • Blood in urine

Call your doctor if these symptoms persist or worsen, especially if there is fever, chills, or other signs of infection.


The placement of a colonic, esophageal, or biliary stent can cause accidental tears or ruptures, leading to pain, bleeding, and infection. Some cases can be severe.

A bowel perforation caused by a colonic stent is associated with a 16% risk of death, mainly due to peritonitis (inflammation of the lining of the abdomen) and sepsis (a whole-body infection). The migration of a stent is also possible due to the constant contractions of the intestines (known as peristalsis).

Esophageal stents can also cause chest pains and gastroesophageal reflux disease (GERD), usually occurring within two to four weeks of the procedure.

In addition to perforation, infection, and stent migration, pancreatic and biliary stents can cause pancreatitis (inflammation of the pancreas) and cholecystitis (inflammation of the gallbladder) in as many as 24% of cases. The risk is greatest if a bare-metal stent is used.


The use of micro-bypass stents has proven to be very safe and effective in people with open-angle glaucoma. Even so, the placement can cause a short-term increase in the intraocular pressure, leading to symptoms such as:

  • Blurred vision
  • Eye redness
  • Seeing halos or colored rings
  • Eye pain with movement or touch

This typically occurs within a month of the procedure but is usually non-severe. Many cases resolve on their own without treatment. Infection, while possible, is uncommon.


Stent technology has changed the way that many diseases are treated today, but they are not for everyone.

In some cases, a condition like coronary artery disease may be more effectively treated with bypass surgery to improve overall blood flow than with a stent that only bridges an obstruction. At other times, the procedure may be contraindicated due to a preexisting health condition.

Some of the contraindications for stenting include:

  • Bleeding disorders, like hemophilia
  • Blood clotting disorders, like antiphospholipid syndrome
  • Hypersensitivity to medications used in drug-eluting stents
  • Hypersensitivity to drugs like Plavix (use to prevent blood clots) or heparin (used to prevent stent encrustation) following stent placement
  • Vessels that are too small or inflexible to accommodate a stent or undergo inflation
  • Evidence of gastrointestinal or esophageal perforation
  • Ascites (the buildup of fluids in the abdomen) in cases of pancreatic or biliary stenting
  • Closed-angle glaucoma in cases of mini-bypass stenting


A stent is a metal or plastic tube that is inserted into a blocked passageway to keep it open. There are different types of stents used in the heart, blood vessels, urinary tract, prostate gland, colon, esophagus, bile ducts, and even the eyes.

Depending on the body part, stenting may require surgery or be applied via a catheter in a vein or during an endoscopic procedure. Risks include the blockage of the stent due to tissue overgrowth or debris as well as perforation of the vessel.

As important as stents are, not everyone can use them. People with bleeding disorders and on certain medications may not be candidates.

A Word From Verywell

Stents have clear advantages over other more invasive forms of treatment. Even so, stents are should not be considered an easy substitute for all medical treatments.

If your doctor advises against a stent, it is usually because the procedure has limitations or is indicated for short-term use only (such as with biliary stenting). If your doctor decides against stenting, ask why and try to keep an open mind. If needed, seek a second opinion from a qualified medical specialist.

14 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Richard N. Fogoros, MD
Richard N. Fogoros, MD, is a retired professor of medicine and board-certified in internal medicine, clinical cardiology, and clinical electrophysiology.