Colonoscopy is more likely to be completed in its entirety when it's performed in the morning than in the afternoon, a Mayo Clinic study shows. The difference in success rates is most likely due differences in the adequacy of bowel cleansing before the procedure.

People undergoing colonoscopy have to purge beforehand, so that the doctor has a clear view of the bowel. The preparation usually starts the evening before the procedure, but this may be too early for an afternoon appointment.

"Consumption of the pre-colonoscopy preparation should be as close as possible to conducting the procedure," Dr. Russell I. Heigh from the Mayo Clinic in Scottsdale, Arizona, told Reuters Health. "At my facility, we offer patients with afternoon colonoscopies a preparation starting very early that same morning."

Heigh and his colleagues evaluated how often colonoscopies were able to traverse the entire bowel, up to the cecum where the colon joins the small intestine, for 3729 colonoscopies performed in the morning and 2358 performed in the afternoon.

The completion rate to the cecum was significantly higher in the morning group (95.0 percent) than in the afternoon group (93.6 percent), the investigators report in the journal BMC Gastroenterology, and the quality of the bowel preparation was also superior in the morning group compared with the afternoon group.

Ways have to be found "to improve afternoon bowel preparation quality ... to reduce the need for repeat examinations," the authors conclude.

"Our next strategy to improve the colonoscopy preparation experience has been to introduce a brochure outlining choices patients and referring physicians have in selecting a pre-colonoscopy prep," Heigh noted.