A randomized controlled trial of four precolonoscopy bowel cleansing regimens

The ideal bowel cleansing regimen for colonoscopy has yet to be determined.

To compare the cleansing efficacy, and patient tolerability and safety of four bowel preparation regimens.

A total of 834 patients undergoing outpatient colonoscopy were randomly assigned to one of four regimens: 4 L polyethylene glycol (PEG); 2 L PEG + 20 mg bisacodyl; 90 mL of sodium phosphate (NaP); or two sachets of a commercially available bowel cleansing solution (PSMC) + 300 mL of magnesium citrate (M). The primary outcome measure was cleansing efficacy, which was scored by blinded endoscopists using the Ottawa Bowel Preparation Scale. Secondary outcome measures were bowel preparation quality according to time of colonoscopy, and patient tolerability and safety.

The mean total cleansing score was significantly worse in the NaP group compared with the other three groups (P<0.0001). The mean cleansing scores were worse in patients who underwent morning versus afternoon colonoscopy, a finding that was consistent in all four groups. PSMC + M was the best tolerated regimen. No clinically significant mean changes in creatinine or electrolyte levels were identified, although a significantly higher proportion of patients in the NaP group developed hypokelemia (P<0.0001).

2 L PEG + 20 mg bisacodyl, or PSMC + M was as efficacious as 4 L PEG and superior to NaP for bowel cleansing. A short interval between the completion of bowel preparation and the start of colonoscopy (ie, 'runway time'), irrespective of bowel preparation regimen, appeared to be a more important predictor of bowel cleanliness than the cathartic agents used.