The first sign of about 1 in 3 bowel cancers is a blockage in the bowel. This is called ’intestinal obstruction’ and causes pain in the gut, sickness, vomiting and constipation. This happens because the bowel becomes narrowed, and blocked, by the presence of the cancer.
Intestinal obstruction usually comes on quite suddenly and often leads to an emergency admission to hospital. Often the problem is eased by an immediate operation, but this is not always a good idea, and putting in a stent is another way of treating the condition.
A stent is a thin metal cylinder, which can be slipped through the narrowed bit of the bowel, where the cancer is, and then expanded to make a rigid tube, which eases the blockage.
There are a number of different stents used for bowel cancer but most are made of a nickel/titanium alloy (called nitinol). To put them in place the patient is given sedation, with an injection into a vein. A colonoscope, which is a sort of flexible telescope, is then passed up through the back passage to where the blockage is. A thin guidewire is slipped through the narrowed bit of bowel, and the stent is threaded over this guide wire. Following this an x-ray is taken to make sure it is in the right position. The stent is then expanded to open up the narrowing in the bowel, and relieve the obstruction.
About 9 times out 10 the stent will be successful in reversing the obstruction and allowing the bowel to work normally again.
In this situation the stent is usually used as a temporary measure. Once things have settled down, and further tests have been done, the usual pattern will be to do an operation to take away the growth (and the stent). Depending on the individual circumstances this may be done a few day or weeks later.
Stents are normally quite safe but very occasionally they can cause complications. These include bleeding from the bowel, or pain, both of which are usually very temporary and settle in a day or two. There is also a small risk that the stent might puncture ( perforate) the bowel when it is being put in place. These problems only affect about 1 in 20 people who have a stent inserted.
Sometimes the stent may not work, either because it is impossible to get it in position in the first place, or because it moves or becomes blocked by the bowel contents. However this is quite uncommon.
Stents are quite a recent development in the treatment of bowel cancer. They have only been used since the late 1990s. At the moment there is a national clinical trial in the UK comparing the use of stents with surgery in the treatment of intestinal obstruction due to bowel cancer. This will give more information on the use of this approach when the results are available in a few years time.