What is a colonoscopy?
A colonoscopy (koh-luh-NAH-skuh-pee) allows a doctor to look inside the entire large intestine. The procedure enables the physician to see things such as inflamed tissue, abnormal growths, and ulcers. It is most often used to look for early signs of cancer in the colon and rectum. It is also used to look for causes of unexplained changes in bowel habits and to evaluate symptoms like abdominal pain, rectal bleeding, and weight loss.

What is the colon? 

The colon, large bowel, or large intestine, is the last portion of your digestive tract, or gastrointestinal tract. The colon is a hollow tube that starts at the end of the small intestine and ends at the rectum and anus. The colon is about 5 feet long, and its main function is to store unabsorbed food waste and absorb water and other body fluids before the waste is eliminated as stool.

Please see the colonscopy prep page for video instruction on how to prepare for your colonoscopy.

For the colonoscopy, you will lie on your left side on the examining table. You will be given pain medication and a sedative to keep you comfortable and help you relax during the exam. 

The doctor will then insert a long, flexible, lighted tube into your rectum and slowly guide it through your colon. The tube is called a colonoscope (koh-LON-oh-skope). The scope transmits an image of the inside of the colon onto a video screen so the doctor can carefully examine the lining of the colon. The scope bends so the doctor can move it around the curves of your colon.
The scope blows air into your colon and inflates it, which helps give the doctor a better view.  Often gentle abdominal pressure is used to help guide the scope.  Most patients do not remember the procedure afterwards.

Colonoscopy allows the doctor to remove polyps from the colon.  Polyps are abnormal growths in the lining of the bowel.  Over time some polyps can evolve into colon cancer.  All polyps seen during a colonoscopy are therefore removed using tiny tools passed through the scope.   The polyps are sent to a lab for testing.  By identifying and removing polyps, a colonoscopy likely prevents most cancers from forming.

The doctor can also remove tissue samples to test in the lab for diseases of the colon (biopsy).  In addition, if any bleeding occurs in the colon, the doctor can pass a laser, heater probe, electrical probe, clipping devices, or special medicines through the scope to stop the bleeding.  The tissue removal and treatments to stop bleeding usually do not cause pain.  In many cases, a colonoscopy allows for accurate diagnosis and treatment of colon abnormalities without the need for a major operation.

History has proven colonoscopy to be a very safe procedure.  Bleeding and puncture of the colon are possible complications but very uncommon.

A colonoscopy usually takes 30 to 60 minutes. The sedative and pain medicine should keep you from feeling much discomfort during the exam.   The great majority of patients do not remember the exam at all.  Afterwards, you may feel some cramping or the sensation of having gas, but it usually stops within an hour.  You will need to remain at the colonoscopy facility for 1 to 2 hours so the sedative can wear off.

Rarely, some people experience severe abdominal pain, fever, bloody bowel movements, dizziness, or weakness afterward.  If you have any of these side effects, contact your physician immediately.  Read your discharge instructions carefully.  Medications such as blood-thinners may need to be stopped for a short time after having your colonoscopy, especially if a biopsy was performed or polyps were removed.  Full recovery by the next day is normal and expected and you may return to your regular activities

Reprinted and modified from the National Digestive Diseases Information Clearinghouse.