I was flabbergasted to learn, as part of the preparation for a colonoscopy, I would not only have to start the bowel clean-out the night before, but would have to get up in the middle of the night to finish the job. If I hadn’t eaten for a day and had dutifully drunk that horrible stuff and suffered the consequences by bedtime, why would I have to do it again in the wee hours?
As everybody of a certain age knows, a colonoscopy is no fun. The doctor inserts a long (very long) viewing tube through the rectum all the way up through the intestines looking for polyps, signs of early colon cancer.
Still, as the 50 percent of us who get the test also know, it’s a lifesaver. Nearly 150,000 of Americans are diagnosed with colon cancer every year, and 55,000 die. Nine times out of 10, colon cancer can be prevented with proper screening.
So colonoscopy is a no-brainer – at least every 10 years starting at age 50.
But why the so-called split-dosing protocol?
Even with no food intake and a good preliminary clean-out, the colon gets mucky overnight. “The other stuff is dead cells, bacterial secretions, mucus, bile, and other material that collect all through the night, even if you have been fasting,” says Dr. John Petrini, a gastroenterologist and immediate past president of the American Society for Gastrointestinal Endoscopy.
Most of this debris winds up on the right side of the colon. “With split-dosing, you get an absolutely clean colon. The right side is particularly clean, which allows you to pick up small polyps that might not otherwise be seen,” Petrini says.
“The reason we do this is not to torture people but to reduce the number of people who need to repeat their tests because of inadequate preparation,” says Dr. Joshua Korzenik, co-director of the Crohn’s and Colitis Center at Massachusetts General Hospital.
That’s why a final clean-out is now often recommended about five hours before the exam. For those who want a colonoscopy first thing in the morning, that means getting up in the middle of the night to finish the prep.