Understanding Colonoscopy

February 19, 2010
Gail M. Wilkes, MS, RNC

The colon, or large intestine, is the last part of the bowel where nutrients are absorbed. Stools are stored in the colon and excreted as a bowel movement.

The colon, or large intestine, is the last part of the bowel where nutrients are absorbed. Stools are stored in the colon and excreted as a bowel movement. Colon cancer is the third leading cause of cancer deaths in the US. It usually starts in the colon or rectum, as a polyp. Most polyps are not cancerous, but polyps called adenomas can become cancer. Colonoscopy can detect polyps early, and remove them. This can prevent polyps from becoming cancer, or cure cancer by taking out a cancerous polyp before it has spread. In the US, it has been estimated that increased awareness of and screening for colon cancer would save at least 30,000 lives each year.

What Is a Colonoscopy?
Colonoscopy is used as a screening test for colon or rectal cancer, and to diagnose symptoms of gastrointestinal disease, including cancer. It is an outpatient procedure, so you will be able to go home on the same day.

Your doctor may recommend colonoscopy for routine screening starting at age 50, or if you have: • A personal or family history of colon cancer • Dark or bloody stools • Unexplained low red blood cell count (anemia) • Persistent and unexplained abdominal pain or diarrhea; and/or • Signifi cant weight loss with gastrointestinal symptoms over a long period of time.

How Do I Prepare for It?
One to three days before, you will drink only clear liquids and will stop eating solid food. On the day before the colonoscopy, you will take special medicine at home to empty or clean out any stool in the colon. It is important to do exactly what you are told, because the colon must be completely clean for the colonoscopy to be accurate. Some medications can interfere with colon cleansing medicines or the colonoscopy itself. Tell your doctor or nurse about your medications and any medication allergies.

What Happens During a Colonoscopy?
On the day of the colonoscopy, you will need someone to take you home afterwards. A sedative or painkiller will be given through a vein before the procedure, to help you feel relaxed. You may feel sleepy. You will lie on your side while the colonoscope, a thin, flexible tube, is inserted into your anus and moved slowly into your colon. Air is passed through the tube to expand the space inside the colon and allow the tube to move forward.

The colonoscope has a light and small video camera that projects images of your colon lining onto a monitor for better viewing. Any polyps usually will be removed during the procedure, and a biopsy, or small bit of tissue, removed to study if there is cancer in it.

What Happens Afterwards?
You will be closely monitored until the medicine side effects have worn off. You will learn the results of the biopsy, if one was done, in about a week.

Normal side effects include bloating, gas, and mild cramps, which usually go away soon after the procedure. You also may have slight bleeding in your stool or from your rectum caused by the biopsy or by polyp removal.

Although very rare, sometimes a small hole can be made in your colon. Call your doctor or go to a hospital emergency department if you have heavy rectal bleeding, severe pain, vomiting, a fever, or a firm, bloated abdomen that does not get better.