1. Home>
2. Specialties>
3. Gastroenterology>
4. Summary and Comment

Morning-Only Bowel Preparation for Afternoon Colonoscopies

Compared with split dosing, morning-only preparation offered equivalent cleansing and better tolerability.

Split dosing (taking half the bowel preparation on the day of colonoscopy) is known to provide superior colon cleansing and is typically better tolerated than taking the entire dose the evening before. To test an extension of the principle that administering a preparation close to the time of colonoscopy is optimal for cleansing, researchers conducted a manufacturer-funded, single-center study of morning-only dosing, in which all the preparation was taken on the day of the procedure.

A total of 116 patients who were scheduled for afternoon colonoscopy were randomized to one of two groups: The morning-only (AM) group received 1 L of polyethylene glycol electrolyte lavage solution 7 hours before colonoscopy and 1 L 4 hours before colonoscopy, and the evening/morning (PM/AM) group received 1 L the evening before and 1 L 4 hours before colonoscopy.

Whole-colon preparation was adequate in 92% of the AM group and 94% of the PM/AM group; right-colon preparation was adequate in 93% and 92% of these groups, respectively. More polyps were detected in the AM group than the PM/AM group (mean, 1.57 vs. 0.94 polyps per patient). The AM group had lower incidence of abdominal pain (P=0.024), better sleep quality (P=0.007), and less interference with the preceding workday (P=0.019) than the PM/AM group. One AM patient (with a body-mass index of 40 kg/m²) aspirated during the procedure, was observed in the hospital for 24 hours, and was treated with 1 week of oral antibiotics.

Comment: Why more polyps were detected in the AM group is unclear, given the similarities in preparation quality. Nonetheless, given what we know about bowel-preparation efficacy, the overall findings make perfect sense. Morning-only bowel preparation should help to improve patient tolerance for afternoon colonoscopy. The episode of aspiration in the morning strikes a cautionary note. But, in my practice, when we use 4-L preps, we give 2 L of preparation on the morning of colonoscopy, and we have not observed an increased incidence of aspiration.

At least for now, these results apply only to 2-L preps. Previous studies have shown that when 4-L preps are used, split dosing tends to be better tolerated than taking the entire dose the evening before. Some caution might also be appropriate for homemade MiraLAX-based preparations, which are 2 L in volume but have lower electrolyte concentrations. In that case, splitting the dose could decrease the theoretical risk for hyponatremia.

— Douglas K. Rex, MD

Published in Journal Watch Gastroenterology October 1, 2010

Citation(s):

Matro R et al. Efficacy of morning-only compared with split-dose polyethylene glycol electrolyte solution for afternoon colonoscopy: A randomized controlled single-blind study. Am J Gastroenterol 2010 Sep; 105:1954.

• Medline abstract (Free)

Reader Remarks:

Review and add to remarks on this article

• colonoscopy prep
  george o chatyrka, mt holly n.j., 18 Jan 2011 11:35 AM EST
  Specialty: Family Medicine
  very thoughtful article.

Image Gallery