Colonoscopy Prep Talk

Having a colonoscopy can be a lifesaver. But if you dread the standard “prep,” there are regimens that are easier and still effective.

It’s essential to clean out your colon adequately before a colonoscopy, so the doctor can see what’s going on inside. If you don’t, the test is more likely to miss polyps and cancerous lesions that may be present, may take longer, and may even have to be redone (along with the prep).

With all regimens, you go on a clear-liquid diet the day before the test. The most common prep involves drinking about 4 quarts of polyethylene glycol solution (such as Golytely or CoLyte), typically half the evening before and half that morning, depending on the time of the test. Available as generics, these are the least expensive and come in various flavors. It’s easiest to drink 8 ounces chilled every 15 to 20 minutes. Lower-volume regimens (such as MoviPrep and HalfLytely) use about 2 quarts of the solution, plus often a standard laxative.

Another option is to schedule the colonoscopy for the afternoon and take the polyethylene glycol solution only that morning (a quart seven hours before the test, then a second quart three hours later). A 2010 study in the American Journal of Gastroenterology found that this abbreviated regimen was as effective as standard split evening/morning dosing and resulted in less abdominal discomfort, less lost sleep, and less interference with the previous workday.

Less commonly used today are sodium phosphate pills. You consume 20 pills and about 40 ounces of liquid the evening before and up to 20 more pills a few hours before the test.

Each method has potential problems. Polyethylene glycol solution can cause bloating and cramps; the unpleasant salty taste can cause nausea. Phosphate pills can cause an electrolyte imbalance, dehydration, and, in rare cases, kidney failure. Thus, the pills carry a black label warning on the package and are generally an option only for healthy people under 60.

Bottom line: Don’t let the prep for colonoscopy scare you away from colorectal cancer screening. Work with your doctor to find a more tolerable regimen, taking into consideration your age and overall health (kidney and gastrointestinal health in particular).

Keep in mind that while colonoscopy is a good screening test for colorectal cancer, it is not necessarily the “best” one. Stool tests (especially fecal immunochemical tests) and sigmoidoscopy remain good options. The key is that everybody age 50 to 75 should be screened for colorectal cancer, whichever test they use.