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New Ways to Diagnose Colon Cancer

Posted Jun 02 2009 4:39pm

New advances in colonoscopy promise faster and easier screenings.

By Colette Bouchez
WebMD Feature
Reviewed by Louise Chang, MD

If you've been putting off having a colonoscopy out of fear or dread, take heart: New advances are helping make this test faster and much easier to endure.

Durado Brooks, MD, director of Colorectal Cancer for the American Cancer Society, tells WebMD that "most people no longer experience any significant discomfort during the procedure. In fact most report they are pretty comfortable," he says.

Gastroenterologist Jennifer Christie, MD, agrees. "Patients are generally much more comfortable now than in the past. And one reason is because doctors are simply getting better at performing this screening. We're better trained and we're doing more procedures, so patients reap the benefits," says Christie, director of Women's Gastrointestinal Health and Motility at Mt. Sinai Medical Center in New York City.

How a Colonoscopy Works

A colonoscopy is one option recommended for screening of colon cancer in adults at average risk. A colonoscopy is performed by inserting a lighted, flexible tube called an endoscope into the rectum to visualize the inside of the colon. The end of the tube houses a tiny camera that relays the images back to a computer screen.

During the test doctors look for lesions known as "polyps." These are small growths that can sometimes be the precursor to colon cancer. If a polyp is found, the endoscope can also be used to remove them during the same procedure.

"In this sense a colonoscopy is both diagnostic and therapeutic -- it can find a problem and treat it during the same procedure," says Brooks.

Advances in Screening Techniques

If you had a colonoscopy in the past -- and didn't find it quite so easy to endure -- chances are your screening did not include the use of a deeper type of sedation that, until recently, was saved for more complex procedures.

"Traditionally we used just a sedative and a narcotic during colonoscopy. Now we're moving towards using an anesthesiologist so that the patient can be put into a deeper sleep without risking safety. And ultimately that means the procedure can be done more quickly and the patient is really very comfortable," says Christie.

Because, however, not all insurance companies will pay for an anesthesiologist, experts say in the future more gastroenterologists will likely be trained in administering anesthesia, particularly in conjunction with a nurse anesthetist.

In addition to more generous use of anesthesia, advances in the instruments used during the test itself are also increasing the comfort level for patients. One such advance helps reduce the incidence of "looping" -- a complication that can make the exam difficult to complete.

In this instance the flexible tubing used to view the inside of the colon gets caught in the multiple internal curves, causing the scope to push against the colon allowing a "loop" to form. This can make it difficult to complete the test.

Advances in Screening Techniques continued...

However, David Lieberman, MD, says several newly designed scopes are helping doctors avoid "looping" in a variety of clever ways.

"One innovation is called a variable fitness instrument -- a scope that allows the doctor to stiffen the head of the scope, making it easier to get through the colon and complete the exam," says Lieberman, chief of gastroenterology at Oregon Health and Science University in Portland.

Additionally, Lieberman tells WebMD that other devices, including one called NeoGuide, use computer chips to remember the turn of the scope, which, he says, also reduces the likelihood of looping.

A brand-new device -- now being tested -- uses balloon technology to push the scope through the colon in a kinder, gentler way.

"It's a dual balloon system with air between them, and it's actually the air pressure that gently advances the endoscope through the colon," says Lieberman, who adds that this too can reduce the possibility of looping.

However, he cautions that most of these new devices are still considered experimental and not yet proven to work in large clinical trials.

"We are definitely heading in this direction, however, and it's all very promising," says Lieberman.

Preparing for Success

In order for a colonoscopy to be successful -- at least in terms of getting a clear visualization -- preparation must include emptying the bowels completely. Many doctors say that achieving this is tantamount to a quick, easy, and successful test.

"The single most important way to increase the success of a colonoscopy is to achieve a good prep. If it's not good, the procedure itself is longer and more difficult to perform," says Lieberman.

In the past this entailed consuming up to a gallon or more of a powerful liquid laxative all within a couple of hours, a task that Christie says many patients found hard to accomplish.

"It's generally not very palatable. Some patients find it very difficult to consume," says Christie.

Now, however, advances are making the prep easier while helping to ensure the success of the screening itself.

Among the newest is OsmoPrep, which offers much of the same bowel cleansing effects as the drink, using half the liquid and no bad taste. The down side: You have to take a lot of pills in a very short period of time.

According to its manufacturer, Salix Pharmaceuticals, the recommended dosage is 32 tablets, divided into doses of four tablets every 15 minutes, each taken with 8 ounces of clear liquid, for a total of 2 quarts. Twenty of the pills are taken the night before the exam, and 12 the day of the test.

"The hope for the future is a totally prepless exam and we are moving in that direction," says Lieberman.

Indeed, Lieberman reports that European studies utilizing an MRI are coming close to achieving this goal.

"With the MRI technology currently being studied in Europe you can theoretically subtract different densities [of material found in the colon] to differentiate between fecal matter and a colon abnormality," says Lieberman.

If the European studies turn out well he estimates the prepless colonoscopy could be a reality within several years.

The Virtual Test

While looking towards the future is promising, there is also one futuristic method of colon screening that is available right now. It's called a "Virtual Colonoscopy" -- a noninvasive screening that uses X-ray beams to look inside the colon.

Doctors say there is so little fuss and bother, the whole procedure is over in less than 10 minutes.

"For the most part, when a patient leaves here they are pleased and happy. They are on and off the table in no time, and there is no sedation. You can literally go back to work in 10 minutes," says Michael Macari, director of abdominal imaging at NYU Medical Center in New York City.

Besides the fact that the screening is noninvasive, Marcari says that prior to the test his center also uses carbon dioxide -- compared with "room air" -- to extend the colon. The difference, he says, means very little cramping and almost no residual pain after the screening is completed.

"Initially there is a little pressure but the carbon dioxide gets absorbed so fast, by the time they leave they feel fine," says Macari.

Looking to the Future

While the screening itself may be fast and easy, right now it requires the same preparation as the regular colonoscopy, so patients are not spared the pretesting discomfort.

However, Macari reports that may change in the not-too-distant future, with the advent of a process called "fecal tagging."

In this procedure, he says, patients drink an agent which -- once inside the colon -- latches onto the fecal material and helps doctors differentiate between that and polyps on the scan.

"We just completed study of 80 patients using fecal tagging and no bowel cleansing and we had a very high rate of detection of polyps over 10 millimeters, which many believe is the real threshold for removal," says Macari.

In another study published in the journal Radiology doctors from Belgium compared fecal tagging with standard colonoscopy preparation. They found that fecal tagging left behind more fecal residue, but improved differentiation of polyps. The fecal tagging also dramatically reduced patient discomfort, side effects, and sleep disturbances.

Still, Marcari says he would not routinely recommend it for virtual colonoscopy -- at least not until larger studies are done.

"Right now it's used if a patient simply cannot tolerate the standard prep, or if a medical condition precludes them from participating in the standard prep," says Macaria.

As easy as a virtual colonoscopy appears to be, Brooks cautions that should a polyp be found during the exam, the patient must still undergo a standard colonoscopy to have the growth removed.

"This requires a second prep and a second procedure whereby if you have the standard colonoscopy screening and something is found, it can be removed on the spot without the need for a second procedure," he says.

Looking to the Future continued...

Macari says that in order to avoid dual prep times some medical centers are coordinating the virtual colonoscopy with a gastroenterologist who is standing by.

"In the event the virtual colonoscopy reveals a problem, the gastroenterlogist is right there ready to perform a standard colonoscopy without the need for a second prep," says Macari.

This dual-system screening is currently being performed in a select number of major medical centers nationwide.

Via: http://www.webmd.com

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