What is a Colonoscopy?
A long, flexible tube (colonoscope) is inserted into the rectum during a colonoscopy. A small video camera at the tip of the tube helps the doctor to view the inside of the whole colon.
Polyps or other types of abnormal tissue can be removed through the scope during a colonoscopy. Tissue samples (biopsies) may be taken during a colonoscopy.
Why am I having a Colonoscopy?
People have colonoscopy for several reasons, such as:
- To investigate intestinal signs and symptoms: Abdominal pain, rectal bleeding, chronic constipation, chronic diarrhea and other intestinal problems.
- Colon Cancer Screening: People age 50 or older who are at risk of colon cancer —your doctor may recommend a colonoscopy every 10 years or sometimes sooner to screen for colon cancer.
- Explore for polyps: People who have had polyps before, maybe recommended a follow-up colonoscopy to look for and remove any additional polyps. This is done to reduce the risk of colon cancer.
What are the risks?
Complications of colonoscopy, such as perforation (making a hole in the bowel wall) or heavy bleeding, are very uncommon. Most surveys report complications in less than 1 in 2000 examinations.
Complications of sedationare also uncommon and include difficulty breathing and abnormal heart rhythms. Serious sedation reactions may be more common in patients with severe heart or chest disease.
What happens during a colonoscopy ?
People getting a colonoscopy will be given a sedative injection through a vein in their arm before the procedure to make them more comfortable.
Doctors will then gently insert the colonoscope through the back passage (anus) and into the large intestine to allow exploration of the entire large bowel.
As cancer of the large bowel arises from pre-existing polyps it is advisable that any polyps found should be removed at the time of the examination. Most polyps are burnt off (this is called polypectomy) by placing a wire snare around the base and applying an electric current.
Most patients do not report significant discomfort from the colonoscopy examination
If a colonoscopy is considered negative, your doctor may recommend that you have another colonoscopy:
- In 10 years
- In five years, only if you have a history of polyps in previous colonoscopy procedures
- In one year, if there was continuous stool in the colon that prevented complete examination of your colon
If the doctor finds any polyps or abnormal tissue in the colon, this is considered a positive.
Not all polyps are cancerous, but some can be precancerous. Polyps removed during colonoscopy are sent to a laboratory for analysis to determine whether they are cancerous, precancerous or noncancerous.
Depending on the size and number of polyps, you may need to follow a more rigorous surveillance schedule in the future to look for more polyps.
If your doctor is concerned about the quality of the view through the scope, he or she may recommend a repeat colonoscopy or a shorter time until your next colonoscopy. If your doctor wasn’t able to advance the scope through your entire colon, a barium enema or virtual colonoscopy may be recommended to examine the rest of your colon.
References: Colorectal Cancer: Screening. U.S. Preventive Services Task Force website.https://www.uspreventiveservicestaskforce.org/Page/Document/UpdateSummaryFinal/colorectal-cancer-screening2 . Updated June 2016. Accessed July 20, 2017.  National Cancer Institute. Colon cancer treatment (PDQ®)-patient version website. https://www.cancer.gov/types/colorectal/patient/colon-treatment-pdq#link/_93 . Updated February 27, 2017. Accessed July 20, 2017.  Lin JS, Piper MA, Perdue LA, et al. Screening for colorectal cancer: updated evidence report and systematic review for the US Preventive Services Task Force. JAMA. 2016;315(23):2576–2594.