How to Prep for a Colonoscopy

5 steps to ease your way to this potentially lifesaving cancer screening

It’s the test most people don’t even want to think about, let alone do. But routine screening colonoscopies—usually every 10 years from age 50 to about 75—can stop colorectal cancer in its tracks.

“The evidence is overwhelmingly positive that the test is effective in preventing colon cancer or identifying patients with asymptomatic colon cancer, when it’s easily cured by surgery,” says J. Sumner Bell III, MD, a gastroenterologist and a spokesman for the American Gastroenterological Association. (“Asymptomatic” means symptoms aren’t showing.)

Colonoscopy is considered the gold standard for colorectal cancer screenings, though there are other options. During a colonoscopy, a doctor inserts a long, flexible, narrow tube inside your rectum and colon. The scope has a light and a tiny camera. During the procedure, suspicious growths, called polyps, can be removed and then tested.

Because it usually involves some level of sedation and a pain reliever, the procedure itself isn’t the part most people dread. It’s the preparation the day before, which calls for a liquid diet and laxatives to clean out your bowels. Bell has some tips to ease the process.

  1. Get a head start.
    Your doctor will probably suggest that you cut back on the fiber in your diet a week or two before the test. That’s because fiber that is nondigestible, such as nuts, whole-wheat grain, brown rice and the skin of fruit, may make prep more difficult. In addition, if you’re prone to constipation, take a laxative for a few days before starting the day-before prep. “It will lower your chances of having inadequate prep,” Bell says.

  2. Adjust for health issues.
    If you have diabetes, take anticoagulants for conditions such as atrial fibrillation, or have other chronic health problems, talk to your doctor ahead of time about ways you might need to customize your prep. And if you had a heart stent inserted or a hip replaced recently, wait six months before having a routine colonoscopy. Older adults or those with mobility issues might want to have someone around to help during prep or consider a bedside commode. “I worry about elderly people rushing to the bathroom and maybe tripping and falling,” Bell says.

  3. Schedule wisely.
    Prep consists of an all-day liquid diet, with laxatives added in the afternoon or evening for a procedure the next morning. Some doctors now use a split dose, so you take half the laxative in the afternoon and wake up around 3 a.m. to take the rest. People with 9-to-5 office jobs usually don’t have to take time off for prep, but those who work outdoors or have a physically demanding job might want to think about the challenges posed by drinking fluids all day without solid food. If you work at night, talk to your doctor about a procedure time and prep schedule that accommodate your needs.

  4. Think about your drinks.
    You can’t eat solid foods during the prep, which means you’ll be taking in plenty of liquids, some mixed with laxatives. It’s still important to make sure you’re drinking enough fluids, and choosing flavors you enjoy can make the prep more palatable. “It’s a good idea to disguise the flavor and the effects of some of the laxatives,” Bell says. “And don’t drink too much cold liquid, or you might start to feel chilled because of how much you need to drink.”

  5. Use soothing ointment.
    Colonoscopy prep causes diarrhea, which can create anal discomfort. After every bowel movement, Bell suggests putting a dab of petroleum jelly or balm on the sensitive area. It’s the grown-up equivalent of preventing diaper rash. 


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