While a good colonoscopy prep rarely tops people's lists of fun things to do, it's an essential part of having a colonoscopy. During a colonoscopy, your doctor inserts a lighted scope into the rectum and advances it through the large and small intestine, looking for polyps, small fleshy growths that can turn cancerous. Restricting certain foods before a colonoscopy leaves less waste in the intestine to be removed during the prep. Realizing the importance of diet and prep before a colonoscopy may make your limited diet options beforehand more palatable.
A colonoscopy allows your doctor to visualize the entire intestinal tract, but a colonoscopy is only as good as the prep. If your prep doesn't really "clean you out," your doctor will have a limited view of the lining of your intestine. If he can't see well, he may miss signs of early cancer. In a February 2004 British study reported in "Gut" that examined 9,223 colonoscopies, poor bowel prep prevented complete visualization of the colon in 19.6 percent of cases.
Some, but not all, physicians impose dietary restrictions starting two days before a scheduled colonoscopy, but even if your doctor doesn't, you may want to consider restricting your diet yourself. A typical dietary restriction starting two days before a colonoscopy allows only liquids in unlimited quantities. Only clear liquids are allowed, no cream soups or dairy products. Do not consume any food or drink that contains red, orange or purple food coloring. Decrease your fiber intake by avoiding fruits, vegetables, nuts, cereals and seeds. Avoid red meat and whole grain pasta.
Red, orange or purple food coloring can stain the sides of the intestine walls, which can look like blood to your doctor during the colonoscopy procedure. Eating no solid food for two days before the procedure reduces the residue in the intestine and the less material you'll need to expel after taking the laxative colon prep the day before the colonoscopy. There's also less likelihood of the colon not emptying completely after the laxative treatment.
A good prep allows easy visualization of the intestinal lining so polyps can be visualized and removed immediately. If polyps are found early, there's less likelihood that they will turn cancerous. It takes approximately 10 years before a small polyp turns cancerous, nurse practitioner Anne Charette of Tufts University reports on UptoDate. Colonoscopy requires several days of prep and the use of sedation. Doing the prep correctly the first time decreases the possibility of a repeat performance because of poor visualization.