Usually performed by a gastroenterologist, a colonoscopy is an examination of the entire length of a patient’s large intestine to look for signs of colon cancer or to treat symptoms such as constipation and diarrhea. If you are experiencing diarrhea, constipation, abdominal pain or rectal bleeding—especially if these symptoms last for more than a couple of weeks—talk to a colonoscopy specialist for a diagnosis. The relatively straight forward procedure may be an uncomfortable topic, but it can be a great way to catch colorectal disease before it has a chance to spread or get worse.

Among experts, colonoscopy is considered to be the best way to maintain colorectal health. Patients should schedule a colonoscopy once every 10 years after they turn 50 years old. If abnormalities are found during one of those screenings—or if you have a history of colorectal disease in your family—you may need to schedule colonoscopies more often than that. Regular screenings are crucial to cancer prevention because the longer a polyp or tumor is left unattended inside the body, the higher the chances it has of becoming cancerous and spreading.

How is a Colonoscopy Performed?

A traditional colonoscopy procedure can last between 30 minutes and 1 hour, depending on whether abnormalities are found and other procedures—such as a polyp removal in the event that a colon polyp is detected—must be performed.

The colonoscopy procedure is done with a colonoscope, a flexible, tube-shaped device about four feet long and less than one inch in diameter. While the patient lies down on a table and pulls his or her knees toward the chest area, the colonoscope is inserted via a patient’s rectum and guided through to the highest section of the large intestine, called the cecum. At the end of the colonoscope, there is a fiber-optic light and a miniature camera, which allow the doctor to capture images of the inside of the patient and display them on a television or computer monitor.

As the colonoscope is guided toward the highest part of the patient’s colon, the doctor can view bowel tissue. However, the more thorough examination is accomplished as the colonoscope is slowly withdrawn.  If abnormalities such as polyps are detected, a colorectal surgeon or proctologist will be able to perform a polyp removal or other form of biopsy during the colonoscopy procedure, by inserting a cutting device into the tubular colonoscope and simply cutting suspicious tissue away.

How Will I Feel During My Colonoscopy?

Patients are always sedated with medication injected via an intravenous line (IV) before the procedure starts. The sedation medication will relax the patient’s muscles and make the patient feel drowsy during the colonoscopy. In fact, many patients claim not to remember much of their colonoscopy procedures as a result of being under the influence of medical sedation. Any pain that might be associated with stretching the colorectal tissue is significantly dulled as a result of the sedation, although the patient may experience stomach cramps, bloating, general abdominal pain or the urge to have a bowel movement.

Since the patient’s bowel will be completely empty after preparation with laxatives and an all-liquid diet the day before the procedure, patients should not worry about passing stool while the colonoscope is inside the colon. Actually, most medical physicians will encourage the patient to pass gas during the procedure, as it will relieve stress and pain and will not affect the results at all.

How Do I Get Ready For a Colonoscopy?

Before patients can undergo colonoscopy, they will need to arrange for a friend or family member to pick them up at the doctor’s office after the procedure. The sedation medication required for colonoscopy has effects that can last for several hours—so it is unsafe to drive after receiving the examination.

Patients also need to practice bowel prep before their procedure. Bowel prep means using drinking several liters of laxative to completely empty the colon during the 1 or 2 days before the colonoscopy. Solid foods must also be avoided. Patients will be advised only to drink clear liquids such as water or lemonade. Unfortunately, bowel prep is oftentimes reported to be the most unappealing part of any colon screening. It is, however, one of the most important aspects of the process and can be a determining factor of whether an accurate diagnosis can be made. Any residual feces left inside the colon might block the doctor’s view of the bowel tissue and could be misconstrued as an irregular growth. Side effects of bowel prep include diarrhea and tiredness, so some patients stay home from work while they prepare their bowel.

Is Getting a Colonoscopy Dangerous?

In general, the risks of a routine colonoscopy are very low. It is a tried method of screening for colon cancer that is almost universally accepted in the medical community as the best, most exhaustive way to detect colon cancer effectively.

However, as with any medical test, there is some risk that complications may arise. Small polyps either obscured by remaining stool or hidden underneath folds on the colorectal wall can be overlooked. Other rare complaints include pain, infection and bleeding. If something is missed, a patient might have to undergo to colonoscopy procedure again. And lastly, there is a slight risk that the bowel tissue will tear (perforation), which would require surgery to fix in the rare case that this occurred. If you have any questions about colonoscopy, bowel prep or whether the risks of colonoscopy are worth the benefits, please discuss your concerns with a gastroenterologist before your procedure.


Reviewed 12/29/2011 by David M. Nolan, M.D.
Diplomate of the American Board of Internal Medicine, 2011
Currently a Fellow of Gastroenterology, at UCI 2011-2014