How to Prepare for a Colonoscopy

A colonoscopy is a common exam that looks inside the large intestine. The large intestine must be empty, clean, and clear so the doctor can see the lining well. When the bowel still holds stool, their view is blocked, and they can’t complete the exam. The steps below explain what a colonoscopy is, how diet should change before the exam, how bowel prep works, and when a colonoscopy is recommended.

Colonoscopy Explained

A colonoscopy is an examination of the large intestine, which includes the colon, rectum, and anus. It uses a colonoscope, a flexible tube with a small lighted camera on the end. A provider inserts the scope through the anus and rectum, then advances it through the colon to where it meets the small intestine. Along the way, the camera sends images to a screen so the lining can be viewed in detail.

The exam serves several purposes. It helps diagnose gastrointestinal diseases, such as inflammatory bowel disease and colorectal cancer, and it can investigate symptoms like rectal bleeding, abdominal pain, or changes in bowel habits. It is also the most sensitive way to screen for colorectal cancer. During the same procedure, a provider can remove polyps or take tissue samples for testing.

Liquid Diet Only

The bowel and rectum need to be empty and clean before the exam. To reach that point, providers commonly recommend a low-fiber diet for two or three days before the procedure. The last day before the procedure requires a clear liquid diet only. Leftover food in the colon blocks the camera’s view and hides parts of the lining. A clear, empty bowel lets the doctor see any abnormalities.

The prep involves laxatives, which cause the body to lose fluid quickly. Clear liquids help replace that fluid and keep the body steady through the process. Common clear liquids include water, broth, and black coffee. 

Bowel Prep

Bowel prep is the step that empties the colon completely. The provider prescribes a laxative solution, usually taken during the afternoon or evening before the procedure. This solution purges the bowels by causing repeated bowel movements over several hours. 

When to Have a Colonoscopy

A colonoscopy can serve more than one role. It may be used for routine cancer screening, for diagnosis, for treatment, or for prevention. Screening is recommended around middle age because the risk of colorectal cancer rises as you get older. Colorectal cancer often causes no symptoms until it is advanced, so screening is the best way to stay ahead of it. If your results are normal and you have no added risk, you may only need the test every 10 years.

You may need one sooner or more often based on your situation. Talk with your provider if you have symptoms such as rectal bleeding, ongoing abdominal pain, or changes in your bowel habits. You may also need earlier or more frequent exams if you have had tissue removed before, have a family history of colorectal cancer, have an inherited condition like familial adenomatous polyposis or Lynch syndrome, or have inflammatory bowel disease.

Ask your provider whether you are due for a colonoscopy and what preparation steps fit your needs.