Differences in Stent Materials and Permanent Versus Temporary Stents

Stents are tubes or tube-like materials used to keep a passageway in the human body open. Most commonly, the passage is a blood vessel, but stents are also used to treat esophageal disorders, kidney blockage, bile duct disorders, and complications of gastrointestinal cancer. Many stents are used with permanency in mind, but re-operation does occur under some circumstances and some conditions benefit more from temporary placement. How long a stent will last in the human body will depend on the exact circumstances of the patient, the type of stent, and the disease or disorder the stent is being used to treat.

Esophageal Stents

Dr. David Johnson, Chief of Gastroenterology at Eastern Virginia Medical School, summarized the guidelines for esophageal stent use for Medscape in March, 2010. Stents are surgically inserted into the esophagus in instances of stricture (constriction and abnormal closure of the esophagus) and obstructive cancer. Based on the extent of disease in the patient and other complications, such as perforation, various types of metal and plastic stents can be used, each with its own potential complications and risk of migration. Ideally the patient would undergo one operation and regain esophageal function without further problems, but some require additional operations to replace or relocate the stent, which decreases the time the stent remains in the body.

In some cases, the stent is only temporarily required to alleviate complications from benign disease (a 2005 study found temporary to be more beneficial over permanent.) Researchers have investigated the best stent types based on the ease and complications of removal from the esophagus, which have been integrated into the guidelines for use. Retrievable esophageal and gastrointestinal stents have shown results after a few weeks to at least 11 months, but the exact timing until removal is dependent on the brand, type, and needs in each patient’s case.

Rectal Stents

A few cases of self-expanding stents have been reported in the alleviation of rectal and intestinal blockages due to inoperable colon cancer. The stents are generally present in the body until the patient’s death, which varies according to the patient and specific circumstances of the cancer. Rectal stents are usually in the body for a few months.

Ureter Stents

Ureter stents are used to assist in the drainage of urine from the kidney by expanding the ducts between the kidney and bladder (the ureters). Placement is usually temporary, but permanent placement may be decided upon if best for the patient’s condition. Temporary stents are removed a few days to 3 months later, or they may pass on their own. Use of temporary ureter stents for more than 3 months can lead to complications.

Bile Duct Stents

Stents are placed in the bile ducts to alleviate blockage of bile flow. According to the University of Southern California’s Center for Pancreatic and Biliary Diseases, plastic stents are used for temporary stenting and metal stents are used for permanent stenting. Hooks on the metal stents reduce the possibility of requiring re-operation, and the stents are expected to remain in the bile ducts for the life of the patient. Plastic stents are used until surgery corrects the condition causing the blockage.

Cardiac Stents

Stents are placed in an artery in the surgical procedure known as angioplasty. An expandable metal meshwork, either bare or coated with a drug eluting material, is placed for permanent support of the artery. Multiple angioplasties may be needed over the course of a patient’s life as other portions of the artery or another artery becomes blocked, leading to multiple stents in the same patient. A complication called restenosis, which occurs within 6 months of the angioplasty, may require replacement of a stent, resulting in a shorter life of the stent in the human body. However, the use of a stent greatly reduces the chance of restenosis compared to the balloon angioplasty without a stent, and the new drug-eluting stents further reduce this risk of requiring replacement. The American Heart Association offers a comparison of interventions for blocked arteries.