Colonoscopy is a procedure used to detect abnormalities in the large intestine (colon). Colonoscopy is the visual inspection of the entire colon (large bowel) from the distal rectum to the cecum. It can show abnormal tissues, ulcers, polyps and cancer.
During a colonoscopy, a colonoscope which is a long, flexible tube with a tiny camera and light source at its tip is inserted into the anus, then the rectum and through the colon to study the inside of the colon. One day before the procedure, it is advised not to eat any solid or semi-solid food, such as mashed potatoes, applesauce, oatmeal, etc. A clear liquid diet must be taken 24 to 72 hours before the procedure. Low-fiber foods that are easy to digest and help empty the bowels may be recommended for three to four days before the procedure.
Why is a colonoscopy done?
A colonoscopy may be recommended to
- Find the cause of gastrointestinal symptoms, such as
- Investigate signs of
- Cancer and other problems
- Identify and remove polyps
- The doctor may recommend a follow-up colonoscopy to investigate and remove any polyps (lumps that can become cancerous).
How often should a colonoscopy be performed?
People with an increased risk of colorectal cancer need a periodic colonoscopy every one to five years. These are people with
- Previous history of polyps or colorectal cancer
- Family history of colorectal cancer
- Inflammatory bowel disease (IBD)
How to prepare for a colonoscopy
Getting ready for colonoscopy is important because the colon must be free of solid matter and be as clean as possible. This will enable the doctor to see the inside of the colon clearly. Any residue in the colon may obstruct the view of the colon and rectum.
- Bowel preparation diet: To clean out or empty the colon, the doctor will give instructions for bowel preparation. This includes
- Eating low-fiber foods that are easy to digest and empty the bowels may be recommended for three to four days before the procedure.
- A clear liquid diet must be eaten 24 to 72 hours before the procedure. Drinks may be limited to clear liquids, such as water, tea and coffee without milk or cream, broth, pulp-free juice, sports drinks and carbonated beverages.
- Any liquids containing red or purple dye must be avoided because they can discolor the colon.
- Solid food should not be eaten the day before the procedure.
- Eating or drinking must not be done after midnight before the procedure.
- Use of laxative: A pill or liquid form of a laxative may be prescribed. This should be taken the night before colonoscopy or both the night before and on the morning of the procedure.
- Enema kit: In some cases, an enema may be used either the night before the procedure or a few hours before the procedure. An enema is only effective in emptying the lower colon.
- Medications: The doctor should be informed about any medications that the patient is taking, including over-the-counter drugs, antibiotics, vitamins or supplements. If the medications can affect the colonoscopy procedure, the doctor may instruct the patient to stop taking certain medications temporarily or may adjust the dosages. These might include
- Allergies: The doctor must be informed about the patient’s allergies and any other medical conditions.
How is a colonoscopy done?
Colonoscopy is performed in a hospital or at an outpatient center. Before the colonoscopy, the patient will be given sedatives through an intravenous (IV) line to minimize any discomfort or pain during the procedure. The patient will be kept as comfortable as possible and vital signs will be continuously monitored.
During the procedure, the patient lies down on the examination table on their left side with their knees drawn up toward the chest. The doctor will insert a colonoscope through the anus and into the rectum and colon.
The colonoscope is long enough to reach the entire length of the colon and contains a light and a tube that allows the doctor to pump air or carbon dioxide to inflate the colon to get a better view of it and its lining. When the scope is moved up or air is pumped, mild cramping may be felt. This can be reduced by taking slow, deep breaths.
The camera on the tip of the colonoscope sends images to an external monitor, allowing the doctor to study the inside of the colon.
A colonoscopy procedure typically takes about 30 to 60 minutes. The procedure may take longer if there are polyps to be removed.